fix(go-server): Allow optional request bodies (#16579)

* fix(go-server): Allow optional request bodies

Closes #16578

* chore: Run scripts

* chore: Remove unnecessary whitespace change

* fix: Use correct error

Author: alex-kuck

modules/openapi-generator/src/main/resources/go-server/controller-api.mustache

@@ -3,6 +3,12 @@ package {{packageName}}
 
 import (
 	"encoding/json"
+    {{#isBodyParam}}
+        {{^required}}
+	"errors"
+	"io"
+        {{/required}}
+    {{/isBodyParam}}
 	"net/http"
 	"strings"
 
@@ -403,7 +409,7 @@ func (c *{{classname}}Controller) {{nickname}}(w http.ResponseWriter, r *http.Re
 	{{^isAdditionalPropertiesTrue}}
 	d.DisallowUnknownFields()
 	{{/isAdditionalPropertiesTrue}}
-	if err := d.Decode(&{{paramName}}Param); err != nil {
+	if err := d.Decode(&{{paramName}}Param); err != nil {{^required}}&& !errors.Is(err, io.EOF) {{/required}}{
 		c.errorHandler(w, r, &ParsingError{Err: err}, nil)
 		return
 	}