| crypto/tls | Package tls partially implements TLS 1.2, as specified in RFC 5246. |
| crypto/x509 | Package x509 parses X.509-encoded keys and certificates. |
| errors | Package errors implements functions to manipulate errors. |
| fmt | Package fmt implements formatted I/O with functions analogous to C's printf and scanf. |
| net | Package net provides a portable interface for network I/O, including TCP/IP, UDP, domain name resolution, and Unix domain sockets. |
| strings | Package strings implements simple functions to manipulate UTF-8 encoded strings. |