v0.2.0 toml-only, harden concurrency and env export, dep updates

constant.go

@@ -31,8 +31,6 @@ const (
 // Format identifiers
 const (
 	FormatTOML = "toml"
-	FormatJSON = "json"
-	FormatYAML = "yaml"
 	FormatAuto = "auto"
 )
 
@@ -62,4 +60,4 @@ const (
 var (
 	DefaultConfigExtensions = []string{".toml", ".conf", ".config"}
 	XDGSystemPaths          = []string{"/etc/xdg", "/etc"}
-)
+)