| fmt | Package fmt implements formatted I/O with functions analogous to C's printf and scanf. |
| github.com/kr/text | Package text provides rudimentary functions for manipulating text in paragraphs. |
| io | Package io provides basic interfaces to I/O primitives. |
| log | Package log implements a simple logging package. |
| 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. |
| text/tabwriter | Package tabwriter implements a write filter (tabwriter.Writer) that translates tabbed columns in input into properly aligned text. |