Assignment to entry in nil map
yourbasic.org/golang
Why does this program panic?
var m map[string]float64
m["pi"] = 3.1416
panic: assignment to entry in nil map
Answer
You have to initialize the map using the make function (or a map literal) before you can add any elements:
m := make(map[string]float64)
m["pi"] = 3.1416
See Maps explained for more about maps.