Overflow

If the result of an arithmetic operation, whether signed or unsigned, has more bits than can be represented in the result type, it is said to overflow.

var u uint8 = 255
fmt.Println(u, u+1, u*u) // "255 0 1"
var i int8 = 127
fmt.Println(i, i+1, i*i) // "127 -128 1"