| flag | Package flag implements command-line flag parsing. |
| fmt | Package fmt implements formatted I/O with functions analogous to C's printf and scanf. |
| go/format | Package format implements standard formatting of Go source. |
| go/token | Package token defines constants representing the lexical tokens of the Go programming language and basic operations on tokens (printing, predicates). |
| golang.org/x/tools/go/analysis | Package analysis defines the interface between a modular static analysis and an analysis driver program. |
| golang.org/x/tools/go/analysis/checker | Package checker provides an analysis driver based on the golang.org/x/tools/go/packages representation of a set of packages and all their dependencies, as produced by packages.Load. |
| golang.org/x/tools/go/analysis/internal/analysisflags | Package analysisflags defines helpers for processing flags of analysis driver tools. |
| golang.org/x/tools/go/packages | Package packages loads Go packages for inspection and analysis. |
| golang.org/x/tools/internal/diff | Package diff computes differences between text files or strings. |
| golang.org/x/tools/internal/robustio | Package robustio wraps I/O functions that are prone to failure on Windows, transparently retrying errors up to an arbitrary timeout. |
| io | Package io provides basic interfaces to I/O primitives. |
| io/ioutil | Package ioutil implements some I/O utility functions. |
| log | Package log implements a simple logging package. |
| os | Package os provides a platform-independent interface to operating system functionality. |
| runtime | Package runtime contains operations that interact with Go's runtime system, such as functions to control goroutines. |
| runtime/pprof | Package pprof writes runtime profiling data in the format expected by the pprof visualization tool. |
| runtime/trace | Package trace contains facilities for programs to generate traces for the Go execution tracer. |
| sort | Package sort provides primitives for sorting slices and user-defined collections. |
| strings | Package strings implements simple functions to manipulate UTF-8 encoded strings. |
| time | Package time provides functionality for measuring and displaying time. |