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.
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.