| encoding | Package encoding defines interfaces shared by other packages that convert data to and from byte-level and textual representations. |
| fmt | Package fmt implements formatted I/O with functions analogous to C's printf and scanf. |
| net/url | Package url parses URLs and implements query escaping. |
| reflect | Package reflect implements run-time reflection, allowing a program to manipulate objects with arbitrary types. |
| strconv | Package strconv implements conversions to and from string representations of basic data types. |
| time | Package time provides functionality for measuring and displaying time. |