Imports of package clean

PathSynopsis
cmd/go/internal/basePackage base defines shared basic pieces of the go command, in particular logging and the Command structure.
cmd/go/internal/cachePackage cache implements a build artifact cache.
cmd/go/internal/cfgPackage cfg holds configuration shared by multiple parts of the go command.
cmd/go/internal/loadPackage load loads packages.
cmd/go/internal/lockedfilePackage lockedfile creates and manipulates files whose contents should only change atomically.
cmd/go/internal/modfetch
cmd/go/internal/modload
cmd/go/internal/strPackage str provides string manipulation utilities.
cmd/go/internal/work
contextPackage context defines the Context type, which carries deadlines, cancellation signals, and other request-scoped values across API boundaries and between processes.
fmtPackage fmt implements formatted I/O with functions analogous to C's printf and scanf.
ioPackage io provides basic interfaces to I/O primitives.
osPackage os provides a platform-independent interface to operating system functionality.
path/filepathPackage filepath implements utility routines for manipulating filename paths in a way compatible with the target operating system-defined file paths.
runtimePackage runtime contains operations that interact with Go's runtime system, such as functions to control goroutines.
strconvPackage strconv implements conversions to and from string representations of basic data types.
stringsPackage strings implements simple functions to manipulate UTF-8 encoded strings.
timePackage time provides functionality for measuring and displaying time.