| fmt | Package fmt implements formatted I/O with functions analogous to C's printf and scanf. |
| go/constant | Package constant implements Values representing untyped Go constants and their corresponding operations. |
| 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. |
| honnef.co/go/tools/lint | |
| honnef.co/go/tools/ssa | |
| math/big | Package big implements arbitrary-precision arithmetic (big numbers). |
| sort | Package sort provides primitives for sorting slices and user-defined collections. |
| strings | Package strings implements simple functions to manipulate UTF-8 encoded strings. |