go micro v2版本中，consul不在默认反对，官网举荐应用etcd，具体起因官网blog有讲https://medium.com/microhq/de...

consul被放到go-plugins, 由社区保护github.com/micro/go-plugins/registry/consul

要应用consul，须要从go-plugins引入

import (    "fmt"    "os"    "context"    "github.com/micro/cli/v2"    proto "github.com/micro/examples/service/proto"    "github.com/micro/go-micro/v2"    "github.com/micro/go-micro/v2/transport/grpc"    "github.com/micro/go-plugins/registry/consul/v2")/*Example usage of top level service initialisation*/type Greeter struct{}func (g *Greeter) Hello(ctx context.Context, req *proto.Request, rsp *proto.Response) error {    rsp.Greeting = "Hello " + req.Name    return nil}func main() {    //reg := consul.NewRegistry()    // Create a new service. Optionally include some options here.    service := micro.NewService(        micro.Name("greeter"),        micro.Version("latest"),        micro.Metadata(map[string]string{            "type": "helloworld",        }),        micro.Registry(reg),        micro.Transport(grpc.NewTransport()),        // Setup some flags. Specify --run_client to run the client        // Add runtime flags        // We could do this below too        micro.Flags(&cli.BoolFlag{            Name:  "run_client",            Usage: "Launch the client",        }),    )    // Init will parse the command line flags. Any flags set will    // override the above settings. Options defined here will    // override anything set on the command line.    service.Init(        // Add runtime action        // We could actually do this above        micro.Action(func(c *cli.Context) error {            if c.Bool("run_client") {                runClient(service)                os.Exit(0)            }            return nil        }),    )    // By default we'll run the server unless the flags catch us    // Setup the server    // Register handler    proto.RegisterGreeterHandler(service.Server(), new(Greeter))    // Run the server    if err := service.Run(); err != nil {        fmt.Println(err)    }}

两种形式应用插件，具体见[go-plugins应用阐明](https://github.com/micro/go-p...

  1. 第一种写到plugins.go中，编译的时候带上plugins

go build -o service ./main.go ./plugins.go

启动时通过命令行参数或环境变量指定

./service --registry=consul

  1. 间接在import中申明，并在micro.NewService()参数中指定，如上文例子

reg := consul.NewRegistry()

micro.Registry(reg),

那么插件是什么时候失效的呢，

micro.NewService()->newService(opts...)->newOptions(opts...)

// Registry sets the registry for the service// and the underlying componentsfunc Registry(r registry.Registry) Option {    return func(o *Options) {        o.Registry = r        // Update router        o.Router.Init(router.Registry(r))        // Update server        o.Server.Init(server.Registry(r))        // Update Broker        o.Broker.Init(broker.Registry(r))    }}

micro.Registry(reg)返回一个匿名函数设置了o.Registry为传进来的r
main()中申明的reg := consul.NewRegistry()，在通过micro.Registry(reg),指定consul为服务发现核心

func newOptions(opts ...Option) Options {    opt := Options{        Auth:      auth.DefaultAuth,        Broker:    broker.DefaultBroker,        Cmd:       cmd.DefaultCmd,        Config:    config.DefaultConfig,        Client:    client.DefaultClient,        Server:    server.DefaultServer,        Store:     store.DefaultStore,        Registry:  registry.DefaultRegistry,        Router:    router.DefaultRouter,        Runtime:   runtime.DefaultRuntime,        Transport: transport.DefaultTransport,        Context:   context.Background(),        Signal:    true,    }    fmt.Println("1", transport.DefaultTransport)    for _, o := range opts {        o(&opt)    }    fmt.Println("2", opt.Transport)    return opt}

在这里顺次调用了micro.NewService()参数中的设置函数设置各项参数，具体能够看下“函数选项模式 Functional Options”，
这里加了2行打印信息能够直观的查看状况，输入是

1 mdns      默认值2 consul    opts设置失效后，变为consul