| bufio | Package bufio implements buffered I/O. It wraps an io.Reader or io.Writer object, creating another object (Reader or Writer) that also implements the interface but provides buffering and some help for textual I/O. |
| internal/testlog | Package testlog provides a back-channel communication path between tests and package os, so that cmd/go can see which environment variables and files a test consults. |
| io | Package io provides basic interfaces to I/O primitives. |
| regexp | Package regexp implements regular expression search. |
| runtime/pprof | Package pprof writes runtime profiling data in the format expected by the pprof visualization tool. |
| strings | Package strings implements simple functions to manipulate UTF-8 encoded strings. |
| sync | Package sync provides basic synchronization primitives such as mutual exclusion locks. |