This says just what it looks like: A ReadWriter can do
what a Reader does and what a Writer
-does; it is a union of the embedded interfaces. The embedding of interfaces
-with overlapping method sets is allowed since Go 1.14: methods from an embedded
-interface may have the same names and identical signatures as methods already
-present in the (embedding) interface. Only interfaces can be embedded within interfaces.
+does; it is a union of the embedded interfaces.
+Only interfaces can be embedded within interfaces.
The same basic idea applies to structs, but with more far-reaching