diff --git a/src/cmd/dist/deps.go b/src/cmd/dist/deps.go
index e4a025701bd..d929252bae8 100644
--- a/src/cmd/dist/deps.go
+++ b/src/cmd/dist/deps.go
@@ -6,14 +6,14 @@ var builddeps = map[string][]string{
 	"bufio":                             {"bytes", "errors", "internal/race", "io", "runtime", "runtime/internal/atomic", "runtime/internal/sys", "sync", "sync/atomic", "unicode", "unicode/utf8"},
 	"bytes":                             {"errors", "internal/race", "io", "runtime", "runtime/internal/atomic", "runtime/internal/sys", "sync", "sync/atomic", "unicode", "unicode/utf8"},
 	"cmd/go/internal/base":              {"bufio", "bytes", "cmd/go/internal/cfg", "cmd/go/internal/str", "context", "errors", "flag", "fmt", "go/ast", "go/build", "go/doc", "go/parser", "go/scanner", "go/token", "internal/race", "internal/syscall/windows", "internal/syscall/windows/registry", "internal/syscall/windows/sysdll", "io", "io/ioutil", "log", "math", "net/url", "os", "os/exec", "os/signal", "path", "path/filepath", "reflect", "regexp", "regexp/syntax", "runtime", "runtime/internal/atomic", "runtime/internal/sys", "sort", "strconv", "strings", "sync", "sync/atomic", "syscall", "text/template", "text/template/parse", "time", "unicode", "unicode/utf16", "unicode/utf8"},
-	"cmd/go/internal/bug":               {"bufio", "bytes", "cmd/go/internal/base", "cmd/go/internal/buildid", "cmd/go/internal/cfg", "cmd/go/internal/env", "cmd/go/internal/load", "cmd/go/internal/str", "cmd/go/internal/web", "cmd/go/internal/work", "compress/flate", "compress/zlib", "container/heap", "context", "crypto", "crypto/sha1", "debug/dwarf", "debug/elf", "debug/macho", "encoding/binary", "errors", "flag", "fmt", "go/ast", "go/build", "go/doc", "go/parser", "go/scanner", "go/token", "hash", "hash/adler32", "internal/race", "internal/syscall/windows", "internal/syscall/windows/registry", "internal/syscall/windows/sysdll", "io", "io/ioutil", "log", "math", "net/url", "os", "os/exec", "os/signal", "path", "path/filepath", "reflect", "regexp", "regexp/syntax", "runtime", "runtime/internal/atomic", "runtime/internal/sys", "sort", "strconv", "strings", "sync", "sync/atomic", "syscall", "text/template", "text/template/parse", "time", "unicode", "unicode/utf16", "unicode/utf8"},
-	"cmd/go/internal/buildid":           {"bufio", "bytes", "cmd/go/internal/cfg", "compress/flate", "compress/zlib", "debug/dwarf", "debug/elf", "debug/macho", "encoding/binary", "errors", "flag", "fmt", "go/ast", "go/build", "go/doc", "go/parser", "go/scanner", "go/token", "hash", "hash/adler32", "internal/race", "internal/syscall/windows", "internal/syscall/windows/registry", "internal/syscall/windows/sysdll", "io", "io/ioutil", "log", "math", "net/url", "os", "path", "path/filepath", "reflect", "regexp", "regexp/syntax", "runtime", "runtime/internal/atomic", "runtime/internal/sys", "sort", "strconv", "strings", "sync", "sync/atomic", "syscall", "text/template", "text/template/parse", "time", "unicode", "unicode/utf16", "unicode/utf8"},
-	"cmd/go/internal/cfg":               {"bufio", "bytes", "errors", "flag", "fmt", "go/ast", "go/build", "go/doc", "go/parser", "go/scanner", "go/token", "internal/race", "internal/syscall/windows", "internal/syscall/windows/registry", "internal/syscall/windows/sysdll", "io", "io/ioutil", "log", "math", "net/url", "os", "path", "path/filepath", "reflect", "regexp", "regexp/syntax", "runtime", "runtime/internal/atomic", "runtime/internal/sys", "sort", "strconv", "strings", "sync", "sync/atomic", "syscall", "text/template", "text/template/parse", "time", "unicode", "unicode/utf16", "unicode/utf8"},
+	"cmd/go/internal/bug":               {"bufio", "bytes", "cmd/go/internal/base", "cmd/go/internal/buildid", "cmd/go/internal/cfg", "cmd/go/internal/envcmd", "cmd/go/internal/load", "cmd/go/internal/str", "cmd/go/internal/web", "cmd/go/internal/work", "compress/flate", "compress/zlib", "container/heap", "context", "crypto", "crypto/sha1", "debug/dwarf", "debug/elf", "debug/macho", "encoding/binary", "errors", "flag", "fmt", "go/ast", "go/build", "go/doc", "go/parser", "go/scanner", "go/token", "hash", "hash/adler32", "internal/race", "internal/syscall/windows", "internal/syscall/windows/registry", "internal/syscall/windows/sysdll", "io", "io/ioutil", "log", "math", "net/url", "os", "os/exec", "os/signal", "path", "path/filepath", "reflect", "regexp", "regexp/syntax", "runtime", "runtime/internal/atomic", "runtime/internal/sys", "sort", "strconv", "strings", "sync", "sync/atomic", "syscall", "text/template", "text/template/parse", "time", "unicode", "unicode/utf16", "unicode/utf8"},
+	"cmd/go/internal/buildid":           {"bufio", "bytes", "cmd/go/internal/cfg", "compress/flate", "compress/zlib", "debug/dwarf", "debug/elf", "debug/macho", "encoding/binary", "errors", "fmt", "go/ast", "go/build", "go/doc", "go/parser", "go/scanner", "go/token", "hash", "hash/adler32", "internal/race", "internal/syscall/windows", "internal/syscall/windows/registry", "internal/syscall/windows/sysdll", "io", "io/ioutil", "log", "math", "net/url", "os", "path", "path/filepath", "reflect", "regexp", "regexp/syntax", "runtime", "runtime/internal/atomic", "runtime/internal/sys", "sort", "strconv", "strings", "sync", "sync/atomic", "syscall", "text/template", "text/template/parse", "time", "unicode", "unicode/utf16", "unicode/utf8"},
+	"cmd/go/internal/cfg":               {"bufio", "bytes", "errors", "fmt", "go/ast", "go/build", "go/doc", "go/parser", "go/scanner", "go/token", "internal/race", "internal/syscall/windows", "internal/syscall/windows/registry", "internal/syscall/windows/sysdll", "io", "io/ioutil", "log", "math", "net/url", "os", "path", "path/filepath", "reflect", "regexp", "regexp/syntax", "runtime", "runtime/internal/atomic", "runtime/internal/sys", "sort", "strconv", "strings", "sync", "sync/atomic", "syscall", "text/template", "text/template/parse", "time", "unicode", "unicode/utf16", "unicode/utf8"},
 	"cmd/go/internal/clean":             {"bufio", "bytes", "cmd/go/internal/base", "cmd/go/internal/buildid", "cmd/go/internal/cfg", "cmd/go/internal/load", "cmd/go/internal/str", "cmd/go/internal/work", "compress/flate", "compress/zlib", "container/heap", "context", "crypto", "crypto/sha1", "debug/dwarf", "debug/elf", "debug/macho", "encoding/binary", "errors", "flag", "fmt", "go/ast", "go/build", "go/doc", "go/parser", "go/scanner", "go/token", "hash", "hash/adler32", "internal/race", "internal/syscall/windows", "internal/syscall/windows/registry", "internal/syscall/windows/sysdll", "io", "io/ioutil", "log", "math", "net/url", "os", "os/exec", "os/signal", "path", "path/filepath", "reflect", "regexp", "regexp/syntax", "runtime", "runtime/internal/atomic", "runtime/internal/sys", "sort", "strconv", "strings", "sync", "sync/atomic", "syscall", "text/template", "text/template/parse", "time", "unicode", "unicode/utf16", "unicode/utf8"},
 	"cmd/go/internal/doc":               {"bufio", "bytes", "cmd/go/internal/base", "cmd/go/internal/cfg", "cmd/go/internal/str", "context", "errors", "flag", "fmt", "go/ast", "go/build", "go/doc", "go/parser", "go/scanner", "go/token", "internal/race", "internal/syscall/windows", "internal/syscall/windows/registry", "internal/syscall/windows/sysdll", "io", "io/ioutil", "log", "math", "net/url", "os", "os/exec", "os/signal", "path", "path/filepath", "reflect", "regexp", "regexp/syntax", "runtime", "runtime/internal/atomic", "runtime/internal/sys", "sort", "strconv", "strings", "sync", "sync/atomic", "syscall", "text/template", "text/template/parse", "time", "unicode", "unicode/utf16", "unicode/utf8"},
-	"cmd/go/internal/env":               {"bufio", "bytes", "cmd/go/internal/base", "cmd/go/internal/buildid", "cmd/go/internal/cfg", "cmd/go/internal/load", "cmd/go/internal/str", "cmd/go/internal/work", "compress/flate", "compress/zlib", "container/heap", "context", "crypto", "crypto/sha1", "debug/dwarf", "debug/elf", "debug/macho", "encoding/binary", "errors", "flag", "fmt", "go/ast", "go/build", "go/doc", "go/parser", "go/scanner", "go/token", "hash", "hash/adler32", "internal/race", "internal/syscall/windows", "internal/syscall/windows/registry", "internal/syscall/windows/sysdll", "io", "io/ioutil", "log", "math", "net/url", "os", "os/exec", "os/signal", "path", "path/filepath", "reflect", "regexp", "regexp/syntax", "runtime", "runtime/internal/atomic", "runtime/internal/sys", "sort", "strconv", "strings", "sync", "sync/atomic", "syscall", "text/template", "text/template/parse", "time", "unicode", "unicode/utf16", "unicode/utf8"},
+	"cmd/go/internal/envcmd":            {"bufio", "bytes", "cmd/go/internal/base", "cmd/go/internal/buildid", "cmd/go/internal/cfg", "cmd/go/internal/load", "cmd/go/internal/str", "cmd/go/internal/work", "compress/flate", "compress/zlib", "container/heap", "context", "crypto", "crypto/sha1", "debug/dwarf", "debug/elf", "debug/macho", "encoding/binary", "errors", "flag", "fmt", "go/ast", "go/build", "go/doc", "go/parser", "go/scanner", "go/token", "hash", "hash/adler32", "internal/race", "internal/syscall/windows", "internal/syscall/windows/registry", "internal/syscall/windows/sysdll", "io", "io/ioutil", "log", "math", "net/url", "os", "os/exec", "os/signal", "path", "path/filepath", "reflect", "regexp", "regexp/syntax", "runtime", "runtime/internal/atomic", "runtime/internal/sys", "sort", "strconv", "strings", "sync", "sync/atomic", "syscall", "text/template", "text/template/parse", "time", "unicode", "unicode/utf16", "unicode/utf8"},
 	"cmd/go/internal/fix":               {"bufio", "bytes", "cmd/go/internal/base", "cmd/go/internal/buildid", "cmd/go/internal/cfg", "cmd/go/internal/load", "cmd/go/internal/str", "compress/flate", "compress/zlib", "context", "crypto", "crypto/sha1", "debug/dwarf", "debug/elf", "debug/macho", "encoding/binary", "errors", "flag", "fmt", "go/ast", "go/build", "go/doc", "go/parser", "go/scanner", "go/token", "hash", "hash/adler32", "internal/race", "internal/syscall/windows", "internal/syscall/windows/registry", "internal/syscall/windows/sysdll", "io", "io/ioutil", "log", "math", "net/url", "os", "os/exec", "os/signal", "path", "path/filepath", "reflect", "regexp", "regexp/syntax", "runtime", "runtime/internal/atomic", "runtime/internal/sys", "sort", "strconv", "strings", "sync", "sync/atomic", "syscall", "text/template", "text/template/parse", "time", "unicode", "unicode/utf16", "unicode/utf8"},
-	"cmd/go/internal/fmt":               {"bufio", "bytes", "cmd/go/internal/base", "cmd/go/internal/buildid", "cmd/go/internal/cfg", "cmd/go/internal/load", "cmd/go/internal/str", "compress/flate", "compress/zlib", "context", "crypto", "crypto/sha1", "debug/dwarf", "debug/elf", "debug/macho", "encoding/binary", "errors", "flag", "fmt", "go/ast", "go/build", "go/doc", "go/parser", "go/scanner", "go/token", "hash", "hash/adler32", "internal/race", "internal/syscall/windows", "internal/syscall/windows/registry", "internal/syscall/windows/sysdll", "io", "io/ioutil", "log", "math", "net/url", "os", "os/exec", "os/signal", "path", "path/filepath", "reflect", "regexp", "regexp/syntax", "runtime", "runtime/internal/atomic", "runtime/internal/sys", "sort", "strconv", "strings", "sync", "sync/atomic", "syscall", "text/template", "text/template/parse", "time", "unicode", "unicode/utf16", "unicode/utf8"},
+	"cmd/go/internal/fmtcmd":            {"bufio", "bytes", "cmd/go/internal/base", "cmd/go/internal/buildid", "cmd/go/internal/cfg", "cmd/go/internal/load", "cmd/go/internal/str", "compress/flate", "compress/zlib", "context", "crypto", "crypto/sha1", "debug/dwarf", "debug/elf", "debug/macho", "encoding/binary", "errors", "flag", "fmt", "go/ast", "go/build", "go/doc", "go/parser", "go/scanner", "go/token", "hash", "hash/adler32", "internal/race", "internal/syscall/windows", "internal/syscall/windows/registry", "internal/syscall/windows/sysdll", "io", "io/ioutil", "log", "math", "net/url", "os", "os/exec", "os/signal", "path", "path/filepath", "reflect", "regexp", "regexp/syntax", "runtime", "runtime/internal/atomic", "runtime/internal/sys", "sort", "strconv", "strings", "sync", "sync/atomic", "syscall", "text/template", "text/template/parse", "time", "unicode", "unicode/utf16", "unicode/utf8"},
 	"cmd/go/internal/generate":          {"bufio", "bytes", "cmd/go/internal/base", "cmd/go/internal/buildid", "cmd/go/internal/cfg", "cmd/go/internal/load", "cmd/go/internal/str", "cmd/go/internal/work", "compress/flate", "compress/zlib", "container/heap", "context", "crypto", "crypto/sha1", "debug/dwarf", "debug/elf", "debug/macho", "encoding/binary", "errors", "flag", "fmt", "go/ast", "go/build", "go/doc", "go/parser", "go/scanner", "go/token", "hash", "hash/adler32", "internal/race", "internal/syscall/windows", "internal/syscall/windows/registry", "internal/syscall/windows/sysdll", "io", "io/ioutil", "log", "math", "net/url", "os", "os/exec", "os/signal", "path", "path/filepath", "reflect", "regexp", "regexp/syntax", "runtime", "runtime/internal/atomic", "runtime/internal/sys", "sort", "strconv", "strings", "sync", "sync/atomic", "syscall", "text/template", "text/template/parse", "time", "unicode", "unicode/utf16", "unicode/utf8"},
 	"cmd/go/internal/get":               {"bufio", "bytes", "cmd/go/internal/base", "cmd/go/internal/buildid", "cmd/go/internal/cfg", "cmd/go/internal/load", "cmd/go/internal/str", "cmd/go/internal/web", "cmd/go/internal/work", "compress/flate", "compress/zlib", "container/heap", "context", "crypto", "crypto/sha1", "debug/dwarf", "debug/elf", "debug/macho", "encoding", "encoding/base64", "encoding/binary", "encoding/json", "encoding/xml", "errors", "flag", "fmt", "go/ast", "go/build", "go/doc", "go/parser", "go/scanner", "go/token", "hash", "hash/adler32", "internal/race", "internal/singleflight", "internal/syscall/windows", "internal/syscall/windows/registry", "internal/syscall/windows/sysdll", "io", "io/ioutil", "log", "math", "net/url", "os", "os/exec", "os/signal", "path", "path/filepath", "reflect", "regexp", "regexp/syntax", "runtime", "runtime/internal/atomic", "runtime/internal/sys", "sort", "strconv", "strings", "sync", "sync/atomic", "syscall", "text/template", "text/template/parse", "time", "unicode", "unicode/utf16", "unicode/utf8"},
 	"cmd/go/internal/help":              {"bufio", "bytes", "cmd/go/internal/base", "cmd/go/internal/cfg", "cmd/go/internal/str", "context", "encoding", "encoding/base64", "encoding/json", "errors", "flag", "fmt", "go/ast", "go/build", "go/doc", "go/parser", "go/scanner", "go/token", "html", "html/template", "internal/race", "internal/syscall/windows", "internal/syscall/windows/registry", "internal/syscall/windows/sysdll", "io", "io/ioutil", "log", "math", "net/url", "os", "os/exec", "os/signal", "path", "path/filepath", "reflect", "regexp", "regexp/syntax", "runtime", "runtime/internal/atomic", "runtime/internal/sys", "sort", "strconv", "strings", "sync", "sync/atomic", "syscall", "text/template", "text/template/parse", "time", "unicode", "unicode/utf16", "unicode/utf8"},
@@ -87,5 +87,5 @@ var builddeps = map[string][]string{
 	"unicode":                 {"runtime", "runtime/internal/atomic", "runtime/internal/sys"},
 	"unicode/utf16":           {"runtime", "runtime/internal/atomic", "runtime/internal/sys"},
 	"unicode/utf8":            {"runtime", "runtime/internal/atomic", "runtime/internal/sys"},
-	"cmd/go":                  {"bufio", "bytes", "cmd/go/internal/base", "cmd/go/internal/bug", "cmd/go/internal/buildid", "cmd/go/internal/cfg", "cmd/go/internal/clean", "cmd/go/internal/doc", "cmd/go/internal/env", "cmd/go/internal/fix", "cmd/go/internal/fmt", "cmd/go/internal/generate", "cmd/go/internal/get", "cmd/go/internal/help", "cmd/go/internal/list", "cmd/go/internal/load", "cmd/go/internal/run", "cmd/go/internal/str", "cmd/go/internal/test", "cmd/go/internal/tool", "cmd/go/internal/version", "cmd/go/internal/vet", "cmd/go/internal/web", "cmd/go/internal/work", "compress/flate", "compress/zlib", "container/heap", "context", "crypto", "crypto/sha1", "debug/dwarf", "debug/elf", "debug/macho", "encoding", "encoding/base64", "encoding/binary", "encoding/json", "encoding/xml", "errors", "flag", "fmt", "go/ast", "go/build", "go/doc", "go/parser", "go/scanner", "go/token", "hash", "hash/adler32", "html", "html/template", "internal/race", "internal/singleflight", "internal/syscall/windows", "internal/syscall/windows/registry", "internal/syscall/windows/sysdll", "io", "io/ioutil", "log", "math", "net/url", "os", "os/exec", "os/signal", "path", "path/filepath", "reflect", "regexp", "regexp/syntax", "runtime", "runtime/internal/atomic", "runtime/internal/sys", "sort", "strconv", "strings", "sync", "sync/atomic", "syscall", "text/template", "text/template/parse", "time", "unicode", "unicode/utf16", "unicode/utf8"},
+	"cmd/go":                  {"bufio", "bytes", "cmd/go/internal/base", "cmd/go/internal/bug", "cmd/go/internal/buildid", "cmd/go/internal/cfg", "cmd/go/internal/clean", "cmd/go/internal/doc", "cmd/go/internal/envcmd", "cmd/go/internal/fix", "cmd/go/internal/fmtcmd", "cmd/go/internal/generate", "cmd/go/internal/get", "cmd/go/internal/help", "cmd/go/internal/list", "cmd/go/internal/load", "cmd/go/internal/run", "cmd/go/internal/str", "cmd/go/internal/test", "cmd/go/internal/tool", "cmd/go/internal/version", "cmd/go/internal/vet", "cmd/go/internal/web", "cmd/go/internal/work", "compress/flate", "compress/zlib", "container/heap", "context", "crypto", "crypto/sha1", "debug/dwarf", "debug/elf", "debug/macho", "encoding", "encoding/base64", "encoding/binary", "encoding/json", "encoding/xml", "errors", "flag", "fmt", "go/ast", "go/build", "go/doc", "go/parser", "go/scanner", "go/token", "hash", "hash/adler32", "html", "html/template", "internal/race", "internal/singleflight", "internal/syscall/windows", "internal/syscall/windows/registry", "internal/syscall/windows/sysdll", "io", "io/ioutil", "log", "math", "net/url", "os", "os/exec", "os/signal", "path", "path/filepath", "reflect", "regexp", "regexp/syntax", "runtime", "runtime/internal/atomic", "runtime/internal/sys", "sort", "strconv", "strings", "sync", "sync/atomic", "syscall", "text/template", "text/template/parse", "time", "unicode", "unicode/utf16", "unicode/utf8"},
 }
diff --git a/src/cmd/go/internal/base/base.go b/src/cmd/go/internal/base/base.go
index 3d04880acdd..aff33f70d8d 100644
--- a/src/cmd/go/internal/base/base.go
+++ b/src/cmd/go/internal/base/base.go
@@ -8,8 +8,6 @@ package base
 
 import (
 	"bytes"
-	"cmd/go/internal/cfg"
-	"cmd/go/internal/str"
 	"errors"
 	"flag"
 	"fmt"
@@ -19,6 +17,9 @@ import (
 	"os/exec"
 	"strings"
 	"sync"
+
+	"cmd/go/internal/cfg"
+	"cmd/go/internal/str"
 )
 
 // A Command is an implementation of a go command
diff --git a/src/cmd/go/internal/base/flag.go b/src/cmd/go/internal/base/flag.go
index 84ea02ad2b9..5e03e640588 100644
--- a/src/cmd/go/internal/base/flag.go
+++ b/src/cmd/go/internal/base/flag.go
@@ -5,8 +5,10 @@
 package base
 
 import (
-	"cmd/go/internal/str"
 	"flag"
+
+	"cmd/go/internal/cfg"
+	"cmd/go/internal/str"
 )
 
 // A StringsFlag is a command-line flag that interprets its argument
@@ -28,6 +30,6 @@ func (v *StringsFlag) String() string {
 
 // AddBuildFlagsNX adds the -n and -x build flags to the flag set.
 func AddBuildFlagsNX(flags *flag.FlagSet) {
-	flags.BoolVar(&BuildN, "n", false, "")
-	flags.BoolVar(&BuildX, "x", false, "")
+	flags.BoolVar(&cfg.BuildN, "n", false, "")
+	flags.BoolVar(&cfg.BuildX, "x", false, "")
 }
diff --git a/src/cmd/go/internal/base/path.go b/src/cmd/go/internal/base/path.go
index f7e985aa596..7a51181c973 100644
--- a/src/cmd/go/internal/base/path.go
+++ b/src/cmd/go/internal/base/path.go
@@ -10,7 +10,15 @@ import (
 	"strings"
 )
 
-var Cwd, _ = os.Getwd()
+func getwd() string {
+	wd, err := os.Getwd()
+	if err != nil {
+		Fatalf("cannot determine current directory: %v", err)
+	}
+	return wd
+}
+
+var Cwd = getwd()
 
 // ShortPath returns an absolute or relative name for path, whatever is shorter.
 func ShortPath(path string) string {
diff --git a/src/cmd/go/internal/cfg/cfg.go b/src/cmd/go/internal/cfg/cfg.go
index 19d648b1938..48b9e81e2da 100644
--- a/src/cmd/go/internal/cfg/cfg.go
+++ b/src/cmd/go/internal/cfg/cfg.go
@@ -7,7 +7,6 @@
 package cfg
 
 import (
-	"flag"
 	"go/build"
 	"os"
 	"path/filepath"
@@ -30,14 +29,18 @@ var (
 	BuildRace              bool               // -race flag
 	BuildToolexec          []string           // -toolexec flag
 	BuildToolchainName     string
-	BuildToolchainCompiler string
-	BuildToolchainLinker   string
+	BuildToolchainCompiler func() string
+	BuildToolchainLinker   func() string
 	BuildV                 bool // -v flag
 	BuildWork              bool // -work flag
 	BuildX                 bool // -x flag
-
 )
 
+func init() {
+	BuildToolchainCompiler = func() string { return "missing-compiler" }
+	BuildToolchainLinker = func() string { return "missing-linker" }
+}
+
 // The test coverage mode affects package loading. Sigh.
 var TestCoverMode string // -covermode flag
 
@@ -50,8 +53,10 @@ type EnvVar struct {
 // OrigEnv is the original environment of the program at startup.
 var OrigEnv []string
 
-// NewEnv is the new environment for running commands.
-var NewEnv []EnvVar
+// CmdEnv is the new environment for running go tool commands.
+// User binaries (during go test or go run) are run with OrigEnv,
+// not CmdEnv.
+var CmdEnv []EnvVar
 
 // Global build parameters (used during package load)
 var (
@@ -61,12 +66,6 @@ var (
 	Gopath    []string
 )
 
-// AddBuildFlagsNX adds the -n and -x build flags to the flag set.
-func AddBuildFlagsNX(flags *flag.FlagSet) {
-	flags.BoolVar(&BuildN, "n", false, "")
-	flags.BoolVar(&BuildX, "x", false, "")
-}
-
 var (
 	GOROOT    = filepath.Clean(runtime.GOROOT())
 	GOBIN     = os.Getenv("GOBIN")
diff --git a/src/cmd/go/internal/clean/clean.go b/src/cmd/go/internal/clean/clean.go
index df57deff1d5..454cac1f47b 100644
--- a/src/cmd/go/internal/clean/clean.go
+++ b/src/cmd/go/internal/clean/clean.go
@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+// Package clean implements the ``go clean'' command.
 package clean
 
 import (
diff --git a/src/cmd/go/internal/doc/doc.go b/src/cmd/go/internal/doc/doc.go
index 512f312fe74..66ff07615ee 100644
--- a/src/cmd/go/internal/doc/doc.go
+++ b/src/cmd/go/internal/doc/doc.go
@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+// Package doc implements the ``go doc'' command.
 package doc
 
 import (
diff --git a/src/cmd/go/internal/env/env.go b/src/cmd/go/internal/envcmd/env.go
similarity index 97%
rename from src/cmd/go/internal/env/env.go
rename to src/cmd/go/internal/envcmd/env.go
index dad158e62cb..c7d8c6cc1be 100644
--- a/src/cmd/go/internal/env/env.go
+++ b/src/cmd/go/internal/envcmd/env.go
@@ -2,7 +2,8 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-package env
+// Package envcmd implements the ``go env'' command.
+package envcmd
 
 import (
 	"fmt"
@@ -103,7 +104,7 @@ func ExtraEnvVars() []cfg.EnvVar {
 }
 
 func runEnv(cmd *base.Command, args []string) {
-	env := cfg.NewEnv
+	env := cfg.CmdEnv
 	env = append(env, ExtraEnvVars()...)
 	if len(args) > 0 {
 		for _, name := range args {
diff --git a/src/cmd/go/internal/fix/fix.go b/src/cmd/go/internal/fix/fix.go
index 0475dc37993..377cd037faf 100644
--- a/src/cmd/go/internal/fix/fix.go
+++ b/src/cmd/go/internal/fix/fix.go
@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+// Package fix implements the ``go fix'' command.
 package fix
 
 import (
diff --git a/src/cmd/go/internal/fmt/fmt.go b/src/cmd/go/internal/fmtcmd/fmt.go
similarity index 93%
rename from src/cmd/go/internal/fmt/fmt.go
rename to src/cmd/go/internal/fmtcmd/fmt.go
index 1124beeedb6..a4bf79e2657 100644
--- a/src/cmd/go/internal/fmt/fmt.go
+++ b/src/cmd/go/internal/fmtcmd/fmt.go
@@ -2,7 +2,8 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-package fmt
+// Package fmtcmd implements the ``go fmt'' command.
+package fmtcmd
 
 import (
 	"os"
@@ -15,7 +16,7 @@ import (
 )
 
 func init() {
-	cfg.AddBuildFlagsNX(&CmdFmt.Flag)
+	base.AddBuildFlagsNX(&CmdFmt.Flag)
 }
 
 var CmdFmt = &base.Command{
diff --git a/src/cmd/go/internal/generate/generate.go b/src/cmd/go/internal/generate/generate.go
index 07f3d139382..fb6d7770918 100644
--- a/src/cmd/go/internal/generate/generate.go
+++ b/src/cmd/go/internal/generate/generate.go
@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+// Package generate implements the ``go generate'' command.
 package generate
 
 import (
diff --git a/src/cmd/go/internal/help/help.go b/src/cmd/go/internal/help/help.go
index 1558fa45879..da52ac00fdf 100644
--- a/src/cmd/go/internal/help/help.go
+++ b/src/cmd/go/internal/help/help.go
@@ -2,17 +2,17 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// Package help implements "go help".
+// Package help implements the ``go help'' command.
 package help
 
 import (
 	"bufio"
 	"bytes"
 	"fmt"
-	"html/template"
 	"io"
 	"os"
 	"strings"
+	"text/template"
 	"unicode"
 	"unicode/utf8"
 
diff --git a/src/cmd/go/internal/list/list.go b/src/cmd/go/internal/list/list.go
index 2f7ae6f72b8..c63753813e6 100644
--- a/src/cmd/go/internal/list/list.go
+++ b/src/cmd/go/internal/list/list.go
@@ -2,19 +2,21 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+// Package list implements the ``go list'' command.
 package list
 
 import (
 	"bufio"
-	"cmd/go/internal/base"
-	"cmd/go/internal/cfg"
-	"cmd/go/internal/load"
-	"cmd/go/internal/work"
 	"encoding/json"
 	"io"
 	"os"
 	"strings"
 	"text/template"
+
+	"cmd/go/internal/base"
+	"cmd/go/internal/cfg"
+	"cmd/go/internal/load"
+	"cmd/go/internal/work"
 )
 
 var CmdList = &base.Command{
diff --git a/src/cmd/go/internal/load/pkg.go b/src/cmd/go/internal/load/pkg.go
index 3b149946cb0..11dd6815df6 100644
--- a/src/cmd/go/internal/load/pkg.go
+++ b/src/cmd/go/internal/load/pkg.go
@@ -883,7 +883,7 @@ func (p *Package) load(stk *ImportStack, bp *build.Package, err error) *Package
 			p.Internal.Target = filepath.Join(cfg.GOROOTpkg, "tool", full)
 		}
 		if p.Internal.Target != "" && cfg.BuildContext.GOOS == "windows" {
-			p.Internal.Target += ".Internal.Exe"
+			p.Internal.Target += ".exe"
 		}
 	} else if p.Internal.Local {
 		// Local import turned into absolute path.
@@ -1562,10 +1562,10 @@ func isStale(p *Package) (bool, string) {
 	// Excluding $GOROOT used to also fix issue 4106, but that's now
 	// taken care of above (at least when the installed Go is a released version).
 	if p.Root != cfg.GOROOT {
-		if olderThan(cfg.BuildToolchainCompiler) {
+		if olderThan(cfg.BuildToolchainCompiler()) {
 			return true, "newer compiler"
 		}
-		if p.Internal.Build.IsCommand() && olderThan(cfg.BuildToolchainLinker) {
+		if p.Internal.Build.IsCommand() && olderThan(cfg.BuildToolchainLinker()) {
 			return true, "newer linker"
 		}
 	}
diff --git a/src/cmd/go/internal/run/run.go b/src/cmd/go/internal/run/run.go
index edd3ddd8432..980e160fee8 100644
--- a/src/cmd/go/internal/run/run.go
+++ b/src/cmd/go/internal/run/run.go
@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+// Package run implements the ``go run'' command.
 package run
 
 import (
@@ -66,7 +67,7 @@ func runRun(cmd *base.Command, args []string) {
 	}
 	for _, file := range files {
 		if strings.HasSuffix(file, "_test.go") {
-			// goFilesPackage is going to assign this to TestGoFiles.
+			// GoFilesPackage is going to assign this to TestGoFiles.
 			// Reject since it won't be part of the build.
 			base.Fatalf("go run: cannot run *_test.go files (%s)", file)
 		}
diff --git a/src/cmd/go/internal/tool/tool.go b/src/cmd/go/internal/tool/tool.go
index 1a3e0765212..51675262e59 100644
--- a/src/cmd/go/internal/tool/tool.go
+++ b/src/cmd/go/internal/tool/tool.go
@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+// Package tool implements the ``go tool'' command.
 package tool
 
 import (
diff --git a/src/cmd/go/internal/version/version.go b/src/cmd/go/internal/version/version.go
index 550f31a3438..c3f7d73ff1d 100644
--- a/src/cmd/go/internal/version/version.go
+++ b/src/cmd/go/internal/version/version.go
@@ -2,12 +2,14 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+// Package version implements the ``go version'' command.
 package version
 
 import (
-	"cmd/go/internal/base"
 	"fmt"
 	"runtime"
+
+	"cmd/go/internal/base"
 )
 
 var CmdVersion = &base.Command{
diff --git a/src/cmd/go/internal/vet/vet.go b/src/cmd/go/internal/vet/vet.go
index fa60d998e13..2bd4fafe95d 100644
--- a/src/cmd/go/internal/vet/vet.go
+++ b/src/cmd/go/internal/vet/vet.go
@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+// Package vet implements the ``go vet'' command.
 package vet
 
 import (
diff --git a/src/cmd/go/internal/work/build.go b/src/cmd/go/internal/work/build.go
index 63731e1dfa6..06611885dac 100644
--- a/src/cmd/go/internal/work/build.go
+++ b/src/cmd/go/internal/work/build.go
@@ -180,8 +180,8 @@ func (c buildCompiler) Set(value string) error {
 		return fmt.Errorf("unknown compiler %q", value)
 	}
 	cfg.BuildToolchainName = value
-	cfg.BuildToolchainCompiler = BuildToolchain.compiler()
-	cfg.BuildToolchainLinker = BuildToolchain.linker()
+	cfg.BuildToolchainCompiler = BuildToolchain.compiler
+	cfg.BuildToolchainLinker = BuildToolchain.linker
 	cfg.BuildContext.Compiler = value
 	return nil
 }
@@ -1317,9 +1317,11 @@ func (b *Builder) build(a *Action) (err error) {
 			sfiles = nil
 		}
 
-		cgoExe := base.Tool("cgo")
+		var cgoExe string
 		if a.cgo != nil && a.cgo.Target != "" {
 			cgoExe = a.cgo.Target
+		} else {
+			cgoExe = base.Tool("cgo")
 		}
 		outGo, outObj, err := b.cgo(a, cgoExe, obj, pcCFLAGS, pcLDFLAGS, cgofiles, objdirCgofiles, gccfiles, cxxfiles, a.Package.MFiles, a.Package.FFiles)
 		if err != nil {
diff --git a/src/cmd/go/main.go b/src/cmd/go/main.go
index 1a9f36b0556..337e0236994 100644
--- a/src/cmd/go/main.go
+++ b/src/cmd/go/main.go
@@ -20,9 +20,9 @@ import (
 	"cmd/go/internal/cfg"
 	"cmd/go/internal/clean"
 	"cmd/go/internal/doc"
-	"cmd/go/internal/env"
+	"cmd/go/internal/envcmd"
 	"cmd/go/internal/fix"
-	fmtcmd "cmd/go/internal/fmt"
+	"cmd/go/internal/fmtcmd"
 	"cmd/go/internal/generate"
 	"cmd/go/internal/get"
 	"cmd/go/internal/help"
@@ -40,7 +40,7 @@ func init() {
 		work.CmdBuild,
 		clean.CmdClean,
 		doc.CmdDoc,
-		env.CmdEnv,
+		envcmd.CmdEnv,
 		bug.CmdBug,
 		fix.CmdFix,
 		fmtcmd.CmdFmt,
@@ -114,8 +114,8 @@ func main() {
 	// but in practice there might be skew
 	// This makes sure we all agree.
 	cfg.OrigEnv = os.Environ()
-	cfg.NewEnv = env.MkEnv()
-	for _, env := range cfg.NewEnv {
+	cfg.CmdEnv = envcmd.MkEnv()
+	for _, env := range cfg.CmdEnv {
 		if os.Getenv(env.Name) != env.Value {
 			os.Setenv(env.Name, env.Value)
 		}