You need
var test = "This is a test"
:=
only works in functions and the lower case ‘t’ is so that it is only visible to the package (unexported).
A more thorough explanation
test1.go
package main
import "fmt"
// the variable takes the type of the initializer
var test = "testing"
// you could do:
// var test string = "testing"
// but that is not idiomatic GO
// Both types of instantiation shown above are supported in
// and outside of functions and function receivers
func main() {
// Inside a function you can declare the type and then assign the value
var newVal string
newVal = "Something Else"
// just infer the type
str := "Type can be inferred"
// To change the value of package level variables
fmt.Println(test)
changeTest(newVal)
fmt.Println(test)
changeTest(str)
fmt.Println(test)
}
test2.go
package main
func changeTest(newTest string) {
test = newTest
}
output
testing
Something Else
Type can be inferred
Alternatively, for more complex package initializations or to set up whatever state is required by the package GO provides an init function.
package main
import (
"fmt"
)
var test map[string]int
func init() {
test = make(map[string]int)
test["foo"] = 0
test["bar"] = 1
}
func main() {
fmt.Println(test) // prints map[foo:0 bar:1]
}
Init will be called before main is run.