add semaphore for goroutine limitation in template

codegen/config/exec.go

@@ -21,7 +21,7 @@ type ExecConfig struct {
 	FilenameTemplate string `yaml:"filename_template,omitempty"` // String template with {name} as placeholder for base name.
 	DirName          string `yaml:"dir"`
 
-	WorkerLimit uint `yaml: "worker_limit"`
+	WorkerLimit uint `yaml:"worker_limit"`
 }
 
 type ExecLayout string

codegen/generated!.gotpl

@@ -10,6 +10,7 @@
 {{ reserveImport "bytes"  }}
 {{ reserveImport "embed"  }}
 
+{{ reserveImport "golang.org/x/sync/semaphore"}}
 {{ reserveImport "github.com/vektah/gqlparser/v2" "gqlparser" }}
 {{ reserveImport "github.com/vektah/gqlparser/v2/ast" }}
 {{ reserveImport "github.com/99designs/gqlgen/graphql" }}

codegen/type.gotpl

@@ -101,6 +101,9 @@
 				ret := make(graphql.Array, len(v))
 				{{- if not $type.IsScalar }}
 					var wg sync.WaitGroup
+					{{- if gt $.Config.Exec.WorkerLimit 0 }}
+						sm := semaphore.NewWeighted({{ $.Config.Exec.WorkerLimit }})
+					{{- end }}
 					isLen1 := len(v) == 1
 					if !isLen1 {
 						wg.Add(len(v))
@@ -124,14 +127,29 @@
 							}()
 							{{- end }}
 							if !isLen1 {
-								defer wg.Done()
+								{{- if gt $.Config.Exec.WorkerLimit 0 }}
+									defer func(){
+										sm.Release(1)
+										wg.Done()
+									}()
+								{{- else }}
+									defer wg.Done()
+								{{- end }}
 							}
 							ret[i] = ec.{{ $type.Elem.MarshalFunc }}(ctx, sel, v[i])
 						}
 						if isLen1 {
 							f(i)
 						} else {
-							go f(i)
+							{{- if gt $.Config.Exec.WorkerLimit 0 }}
+								if err := sm.Acquire(ctx, 1); err != nil {
+									ec.Error(ctx, ctx.Err())
+								} else {
+									go f(i)
+								}
+							{{- else }}
+								go f(i)
+							{{- end }}
 						}
 					{{ else }}
 						ret[i] = ec.{{ $type.Elem.MarshalFunc }}(ctx, sel, v[i])