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

Package cpu implements processor feature detection used by the Go standard library.

Package fmtsort provides a general stable ordering mechanism for maps, on behalf of the fmt and text/template packages.

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

Package lazytemplate is a thin wrapper over text/template, allowing the use of global template variables without forcing them to be parsed at init.

Package nettrace contains internal hooks for tracing activity in the net package.

Package obscuretestdata contains functionality used by tests to more easily work with testdata that must be obscured primarily due to golang.org/issue/34986.

Package oserror defines errors values used in the os package.

Package poll supports non-blocking I/O on file descriptors with polling.

Package race contains helper functions for manually instrumenting code for the race detector.

Package reflectlite implements lightweight version of reflect, not using any package except for "runtime" and "unsafe".

Package singleflight provides a duplicate function call suppression mechanism.

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

Package testlog provides a back-channel communication path between tests and package os, so that cmd/go can see which environment variables and files a test consults.

Package xcoff implements access to XCOFF (Extended Common Object File Format) files.