fmt | Package fmt implements formatted I/O with functions analogous to C's printf and scanf. |
go/ast | Package ast declares the types used to represent syntax trees for Go packages. |
go/build | Package build gathers information about Go packages. |
go/parser | Package parser implements a parser for Go source files. |
go/token | Package token defines constants representing the lexical tokens of the Go programming language and basic operations on tokens (printing, predicates). |
go/types | Package types declares the data types and implements the algorithms for type-checking of Go packages. |
io | Package io provides basic interfaces to I/O primitives. |
os | Package os provides a platform-independent interface to operating system functionality. |
path/filepath | Package filepath implements utility routines for manipulating filename paths in a way compatible with the target operating system-defined file paths. |
sync | Package sync provides basic synchronization primitives such as mutual exclusion locks. |