chore(lint): fixing some linter errors

Makefile

@@ -2,7 +2,7 @@ build:
  $(MAKE) -C testdata/hello-go build
 
 tests: build
- go test --race -v -covermode=atomic -coverprofile=coverage.out ./...
+ go test -race -v -covermode=atomic -coverprofile=coverage.out ./...
 
 benchmarks: build
  go test -bench=. -benchmem ./...

callbacks/router_test.go

@@ -33,7 +33,7 @@ func (c *Counter) Reset() {
  c.count = 0
 }
 
-var ErrTestError = fmt.Errorf("test error")
+var ErrTestError = errors.New("test error")
 
 type RouterTestCase struct {
  Name string
@@ -377,7 +377,7 @@ func ExampleNew() {
  Namespace: "example",
  Capability: "greeting",
  Operation: "hello",
- Func: func(input []byte) ([]byte, error) {
+ Func: func(_ []byte) ([]byte, error) {
  fmt.Println("Hello World!")
  return []byte(""), nil
  },

engine/module.go

@@ -2,6 +2,7 @@ package engine
 
 import (
  "context"
+ "errors"
  "fmt"
  "time"
 
@@ -10,7 +11,7 @@ import (
 
 var (
  // ErrInvalidModuleConfig is returned when a ModuleConfig is invalid.
- ErrInvalidModuleConfig = fmt.Errorf("invalid module config")
+ ErrInvalidModuleConfig = errors.New("invalid module config")
 )
 
 const (

engine/wasm.go

@@ -20,6 +20,7 @@ package engine
 
 import (
  "context"
+ "errors"
  "fmt"
  "os"
  "sync"
@@ -30,7 +31,10 @@ import (
 
 var (
  // ErrModuleNotFound is returned when a module is not found.
- ErrModuleNotFound = fmt.Errorf("module not found")
+ ErrModuleNotFound = errors.New("module not found")
+
+ // ErrCallbackNil is returned when the callback function is nil.
+ ErrCallbackNil = errors.New("callback cannot be nil")
 )
 
 // ServerConfig is used to configure the initial Server.
@@ -65,7 +69,7 @@ func New(cfg ServerConfig) (*Server, error) {
  s.modules = make(map[string]*Module)
 
  if cfg.Callback == nil {
- return s, fmt.Errorf("callback cannot be nil")
+ return s, ErrCallbackNil
  }
 
  s.callback = cfg.Callback