当我尝试调用 API 时，本地服务器返回“http：恐慌服务：52781：运行时错误：无效的内存地址或 nil 指针取消引用”

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我按照指南在这里编写了 mongodb API： https://www.thepolyglotdeveloper.com/2019/02/developing-restful-api-golang-mongodb-nosql-database/

该指南的代码运行完美。但是，当我尝试将代码拆分成小包以添加更多案例并更易于阅读时，服务器总是作为标题返回。下面是代码，我只是将指南的代码分成小包，不添加任何新内容或删除任何内容。我做错了什么或者我错过了什么？ https://github.com/imperiustx/mongo_golang

解决方案

您遇到此问题是因为 middleware.go 文件中的 client 变量为零。

client 在这里是一个依赖项。它必须从main包注入到middleware包。

修复：-

中间件.go

type endpoints struct {
    client *mongo.client
}

func newendpoints(client *mongo.client) *endpoints {
    return &endpoints{
        client: client,
    }
}

func (e *endpoints) createpersonendpoint(response http.responsewriter, request *http.request) {
    response.header().set("content-type", "application/json")
    var person models.person
    _ = json.newdecoder(request.body).decode(&person)
    collection := e.client.database("thepolyglotdeveloper").collection("people")
    ctx, cancel := context.withtimeout(context.background(), 5*time.second)
    defer cancel()
    result, _ := collection.insertone(ctx, person)
    json.newencoder(response).encode(result)
}
func (e *endpoints) getpeopleendpoint(response http.responsewriter, request *http.request) {
    response.header().set("content-type", "application/json")
    var people []models.person
    collection := e.client.database("thepolyglotdeveloper").collection("people")
    ctx, cancel := context.withtimeout(context.background(), 30*time.second)
    defer cancel()
    cursor, err := collection.find(ctx, bson.m{})
    if err != nil {
        response.writeheader(http.statusinternalservererror)
        response.write([]byte(`{ "message": "` + err.error() + `" }`))
        return
    }
    defer cursor.close(ctx)
    for cursor.next(ctx) {
        var person models.person
        cursor.decode(&person)
        people = append(people, person)
    }
    if err := cursor.err(); err != nil {
        response.writeheader(http.statusinternalservererror)
        response.write([]byte(`{ "message": "` + err.error() + `" }`))
        return
    }
    json.newencoder(response).encode(people)
}
func (e *endpoints) getpersonendpoint(response http.responsewriter, request *http.request) {
    response.header().set("content-type", "application/json")
    params := mux.vars(request)
    id, _ := primitive.objectidfromhex(params["id"])
    var person models.person
    collection := e.client.database("thepolyglotdeveloper").collection("people")
    ctx, cancel := context.withtimeout(context.background(), 30*time.second)
    defer cancel()
    err := collection.findone(ctx, models.person{id: id}).decode(&person)
    if err != nil {
        response.writeheader(http.statusinternalservererror)
        response.write([]byte(`{ "message": "` + err.error() + `" }`))
        return
    }
    json.newencoder(response).encode(person)
}

main.go

func main() {
    fmt.Println("Starting the application...")
    ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
    defer cancel()
    clientOptions := options.Client().ApplyURI("mongodb://localhost:27017")
    client, _ = mongo.Connect(ctx, clientOptions)

    endpoints := middleware.NewEndpoints(client) // injecting the dependency
    router := mux.NewRouter()
    router.HandleFunc("/person", endpoints.CreatePersonEndpoint).Methods("POST")
    router.HandleFunc("/people", endpoints.GetPeopleEndpoint).Methods("GET")
    router.HandleFunc("/person/{id}", endpoints.GetPersonEndpoint).Methods("GET")
    http.ListenAndServe(":12345", router)
}

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