strconv provides functions for converting strings to numbers and numbers to strings.
write_dec and write_dec_u write a decimal integer into a caller-provided []u8
buffer. They return the number of bytes written, or -1 when the buffer is too small.
import strconv
mut buf := []u8{len: 20}
n := strconv.write_dec(-12345, mut buf)
assert n == 6
assert buf[..n].bytestr() == '-12345'