no need for a custom decoder

internal/gcp/clusters.go

@@ -1,12 +1,10 @@
 package gcp
 
 import (
+	"bytes"
 	"encoding/json"
 	"fmt"
 	"strconv"
-	"strings"
-
-	"github.com/sethvargo/go-envconfig"
 )
 
 type (
@@ -17,19 +15,19 @@ type (
 	}
 )
 
-var _ envconfig.Decoder = (*Clusters)(nil)
+var _ json.Unmarshaler = (*Clusters)(nil)
 
-func (c *Clusters) EnvDecode(value string) error {
-	*c = make(Clusters)
-	if value == "" {
+func (c *Clusters) UnmarshalJSON(value []byte) error {
+	if len(value) == 0 {
 		return nil
 	}
 	clustersWithStringID := make(map[string]struct {
 		TeamsFolderID string `json:"teams_folder_id"`
 		ProjectID     string `json:"project_id"`
 	})
 
-	err := json.NewDecoder(strings.NewReader(value)).Decode(&clustersWithStringID)
+	*c = make(Clusters)
+	err := json.NewDecoder(bytes.NewReader(value)).Decode(&clustersWithStringID)
 	if err != nil {
 		return fmt.Errorf("parse GCP cluster info: %w", err)
 	}

internal/gcp/clusters_test.go

@@ -10,7 +10,7 @@ func TestDecodeJSONToClusters(t *testing.T) {
 	clusters := make(gcp.Clusters)
 
 	t.Run("empty string", func(t *testing.T) {
-		err := clusters.EnvDecode("")
+		err := clusters.UnmarshalJSON([]byte(""))
 		if err != nil {
 			t.Fatalf("unexpected error: %v", err)
 		}
@@ -21,7 +21,7 @@ func TestDecodeJSONToClusters(t *testing.T) {
 	})
 
 	t.Run("empty JSON object", func(t *testing.T) {
-		err := clusters.EnvDecode("{}")
+		err := clusters.UnmarshalJSON([]byte("{}"))
 		if err != nil {
 			t.Fatalf("unexpected error: %v", err)
 		}
@@ -32,10 +32,10 @@ func TestDecodeJSONToClusters(t *testing.T) {
 	})
 
 	t.Run("JSON with clusters", func(t *testing.T) {
-		err := clusters.EnvDecode(`{
+		err := clusters.UnmarshalJSON([]byte(`{
 			"env1": {"teams_folder_id": "123", "project_id": "some-id-123"},
 			"env2": {"teams_folder_id": "456", "project_id": "some-id-456"}
-		}`)
+		}`))
 		if err != nil {
 			t.Fatalf("unexpected error: %v", err)
 		}