Cannot always get reflect info for func signature in Go

I have this which returns a string representation of a function signature:

func getFuncSignature(v interface{}) string {

    funcValue := reflect.ValueOf(v)
    funcType := funcValue.Type()
    name := funcType.Name()

    // Function signature
    var params []string
    for i := 0; i < funcType.NumIn(); i++ {
        nm := funcType.In(i).Name()
        if strings.TrimSpace(nm) == "" {
            nm = "<unk>"    // <<<<<<<<<<<<<<<<<<<<< HERE 1
        }
        params = append(params, nm)
    }

    var returns []string
    for i := 0; i < funcType.NumOut(); i++ {
        nm := funcType.Out(i).Name()
        if strings.TrimSpace(nm) == "" {
            nm = "<unk>"  // <<<<<<<<<<<<<<<<<<<<<< HERE 2
        }
        returns = append(returns, nm)
    }

    paramsStr := strings.Join(params, ", ")
    returnsStr := strings.Join(returns, ", ")

    if name != "" {
        return fmt.Sprintf("(func %s(%s) => (%s))", name, paramsStr, returnsStr)
    }

    return fmt.Sprintf("(func(%s) => (%s))", paramsStr, returnsStr)
}

however, some parameter and return types return empty strings, so I put in "" which isn't really ideal. Is there some way to retrieve the names/types of the input and return values?