envexp: turn Expander from interface to struct

Signed-off-by: Alejandro Mery <amery@jpi.io>

envexp/expand.go

@@ -10,34 +10,30 @@ import (
 type VarGetter func(key string) string
 
 // A Expander is an object that you can use to Expand strings
-type Expander interface {
-	Expand(s string) string
-}
-
-type expander struct {
+type Expander struct {
 	get VarGetter
 }
 
 // NewExpander allocates a new Expander using a
 // given VarGetter, or os.Getenv if none is given
-func NewExpander(f VarGetter) Expander {
+func NewExpander(f VarGetter) *Expander {
 	if f == nil {
 		f = os.Getenv
 	}
 
-	return &expander{
+	return &Expander{
 		get: f,
 	}
 }
 
 // Get resolves a variable name as the given Expander
 // would do
-func (exp *expander) Get(key string) string {
+func (exp *Expander) Get(key string) string {
 	return exp.get(key)
 }
 
 // Expand expands a string using the VarGetter
 // defined for the given Expander
-func (exp *expander) Expand(s string) string {
+func (exp *Expander) Expand(s string) string {
 	return s
 }

envexp/global.go

@@ -4,7 +4,7 @@ import (
 	"os"
 )
 
-var envExpander = &expander{
+var envExpander = &Expander{
 	get: os.Getenv,
 }