Prevent redundant type assertion in Get

There is no need to assert variables which already have appropriate
type.

name              old time/op    new time/op    delta
GetBool-4            554ns ± 3%     493ns ± 8%  -10.86%  (p=0.000 n=14+15)
Get-4                484ns ± 4%     414ns ± 7%  -14.37%  (p=0.000 n=14+15)
GetBoolFromMap-4    8.38ns ± 6%    7.83ns ± 7%   -6.59%  (p=0.000 n=15+15)

name              old alloc/op   new alloc/op   delta
GetBool-4            65.0B ± 0%     64.0B ± 0%   -1.54%  (p=0.000 n=15+15)
Get-4                64.0B ± 0%     64.0B ± 0%     ~     (all equal)
GetBoolFromMap-4     0.00B          0.00B          ~     (all equal)

name              old allocs/op  new allocs/op  delta
GetBool-4             5.00 ± 0%      4.00 ± 0%  -20.00%  (p=0.000 n=15+15)
Get-4                 5.00 ± 0%      4.00 ± 0%  -20.00%  (p=0.000 n=15+15)
GetBoolFromMap-4      0.00           0.00          ~     (all equal)

viper.go

@@ -53,7 +53,7 @@ func init() {
 type remoteConfigFactory interface {
 	Get(rp RemoteProvider) (io.Reader, error)
 	Watch(rp RemoteProvider) (io.Reader, error)
-	WatchChannel(rp RemoteProvider)(<-chan *RemoteResponse, chan bool)
+	WatchChannel(rp RemoteProvider) (<-chan *RemoteResponse, chan bool)
 }
 
 // RemoteConfig is optional, see the remote package
@@ -597,32 +597,33 @@ func (v *Viper) Get(key string) interface{} {
 		return nil
 	}
 
-	valType := val
 	if v.typeByDefValue {
 		// TODO(bep) this branch isn't covered by a single test.
+		valType := val
 		path := strings.Split(lcaseKey, v.keyDelim)
 		defVal := v.searchMap(v.defaults, path)
 		if defVal != nil {
 			valType = defVal
 		}
+
+		switch valType.(type) {
+		case bool:
+			return cast.ToBool(val)
+		case string:
+			return cast.ToString(val)
+		case int64, int32, int16, int8, int:
+			return cast.ToInt(val)
+		case float64, float32:
+			return cast.ToFloat64(val)
+		case time.Time:
+			return cast.ToTime(val)
+		case time.Duration:
+			return cast.ToDuration(val)
+		case []string:
+			return cast.ToStringSlice(val)
+		}
 	}
 
-	switch valType.(type) {
-	case bool:
-		return cast.ToBool(val)
-	case string:
-		return cast.ToString(val)
-	case int64, int32, int16, int8, int:
-		return cast.ToInt(val)
-	case float64, float32:
-		return cast.ToFloat64(val)
-	case time.Time:
-		return cast.ToTime(val)
-	case time.Duration:
-		return cast.ToDuration(val)
-	case []string:
-		return cast.ToStringSlice(val)
-	}
 	return val
 }