- Package bytes implements functions for the manipulation of byte slices.
It is analogous to the facilities of the strings package. 
- compat module contains functions that ease porting of Go code to Rust.
These functions are intended for internal usage only. 
- Package errors implements functions to manipulate errors. 
- Package hash provides interfaces for hash functions. 
- Package image implements a basic 2-D image library. 
- Package io provides basic interfaces to I/O primitives.
Its primary job is to wrap existing implementations of such primitives,
such as those in package os, into shared public interfaces that
abstract the functionality, plus some other related primitives. 
- Package strconv implements conversions to and from string representations
of basic data types. 
- Package time provides functionality for measuring and displaying time. 
- Package unicode provides data and functions to test some properties of
Unicode code points.