| bytes | Package bytes implements functions for the manipulation of byte slices. |
| crypto/rand | Package rand implements a cryptographically secure random number generator. |
| crypto/rsa | Package rsa implements RSA encryption as specified in PKCS #1 and RFC 8017. |
| crypto/sha1 | Package sha1 implements the SHA-1 hash algorithm as defined in RFC 3174. |
| crypto/tls | Package tls partially implements TLS 1.2, as specified in RFC 5246, and TLS 1.3, as specified in RFC 8446. |
| crypto/x509 | Package x509 implements a subset of the X.509 standard. |
| crypto/x509/pkix | Package pkix contains shared, low level structures used for ASN.1 parsing and serialization of X.509 certificates, CRL and OCSP. |
| errors | Package errors implements functions to manipulate errors. |
| log | Package log implements a simple logging package. |
| math/big | Package big implements arbitrary-precision arithmetic (big numbers). |
| net | Package net provides a portable interface for network I/O, including TCP/IP, UDP, domain name resolution, and Unix domain sockets. |
| sync | Package sync provides basic synchronization primitives such as mutual exclusion locks. |
| time | Package time provides functionality for measuring and displaying time. |