JuniorTheoryCommon

What happens when this program is built and run?

package main

import "fmt"

func main() {
    var m map[string]int
    fmt.Println(len(m))
    m["a"] = 1
    fmt.Println(m)
}

Prints 0, then panics

Expecting map[a:1], as if the first write created the map: a declared map is nil, and writing to it panics with assignment to entry in nil map.
Expecting len(m) to panic: reading a nil map is safe, it behaves as an empty map, so len(m) is 0 and the panic comes only on the write.

JuniorTheoryCommon

package main

import "fmt"

func main() {
    var m map[string]int
    fmt.Println(len(m))
    m["a"] = 1
    fmt.Println(m)
}

Prints 0, then panics

Expecting map[a:1], as if the first write created the map: a declared map is nil, and writing to it panics with assignment to entry in nil map.
Expecting len(m) to panic: reading a nil map is safe, it behaves as an empty map, so len(m) is 0 and the panic comes only on the write.