Package cfg holds configuration shared by the Go command and internal/testenv.

Package execabs is a drop-in replacement for os/exec that requires PATH lookups to find absolute paths.

Package lazyregexp is a thin wrapper over regexp, allowing the use of global regexp variables without forcing them to be compiled at init.

Package testenv provides information about what functionality is available in different testing environments run by the Go team.

Package unsafeheader contains header declarations for the Go runtime's slice and string implementations.