How to get a value from map - go

Question

Problem
Fetching data from map
Data Format
res = map[Event_dtmReleaseDate:2009-09-15 00:00:00 +0000 +00:00 Trans_strGuestList:<nil> strID:TSTB]
Note
How to get the following value from the above result
Event_dtmReleaseDate
strID
Trans_strGuestList
What i tried:
res.Map("Event_dtmReleaseDate");
Error : res.Map undefined (type map[string]interface {} has no field or method Map)
res.Event_dtmReleaseDate;
Error: v.id undefined (type map[string]interface {} has no field or method id)

Answer 1

Your variable is a map[string]interface {} which means the key is a string but the value can be anything. In general the way to access this is:
mvVar := myMap[key].(VariableType)
Or in the case of a string value:
id := res["strID"].(string)
Note that this will panic if the type is not correct or the key does not exist in the map, but I suggest you read more about Go maps and type assertions.
Read about maps here: http://golang.org/doc/effective_go.html#maps
And about type assertions and interface conversions here: http://golang.org/doc/effective_go.html#interface_conversions
The safe way to do it without a chance to panic is something like this:
var id string
var ok bool
if x, found := res["strID"]; found {
if id, ok = x.(string); !ok {
//do whatever you want to handle errors - this means this wasn't a string
}
} else {
//handle error - the map didn't contain this key
}

Answer 2

In general to get value from map you have to do something like this:
package main
import "fmt"
func main() {
m := map[string]string{"foo": "bar"}
value, exists := m["foo"]
// In case when key is not present in map variable exists will be false.
fmt.Printf("key exists in map: %t, value: %v \n", exists, value)
}
Result will be:
key exists in map: true, value: bar