| 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. |
| golang.org/x/tools/internal/astutil/edge | Package edge defines identifiers for each field of an ast.Node struct type that refers to another Node. |
| iter | Package iter provides basic definitions and operations related to iterators over sequences. |
| math | Package math provides basic constants and mathematical functions. |
| unsafe | Package unsafe contains operations that step around the type safety of Go programs. |