| errors | Package errors implements functions to manipulate errors. |
| golang.org/x/text/encoding/internal/identifier | Package identifier defines the contract between implementations of Encoding and Index by defining identifiers that uniquely identify standardized coded character sets (CCS) and character encoding schemes (CES), which we will together refer to as encodings, for which Encoding implementations provide converters to and from UTF-8. |
| golang.org/x/text/transform | Package transform provides reader and writer wrappers that transform the bytes passing through as well as various transformations. |
| io | Package io provides basic interfaces to I/O primitives. |
| strconv | Package strconv implements conversions to and from string representations of basic data types. |
| unicode/utf8 | Package utf8 implements functions and constants to support text encoded in UTF-8. |