Confusions and solutions encountered when using the golang framework

The following are common confusing questions and their answers in Go framework development: Database connection error: Use the Create method instead of the CreateDatabase method. Null field error: Ensure null fields are nullable (string: string, time: *time.Time). Error getting model ID: Make sure the model structure has a primary key field. Transaction error: "tx has been committed or rolled back": Ensure that no errors occurred during processing, rollback on failure and commit on success. httprouter route handler context: Access the request context through the httprouter.ParamsFromContext function.

Confusion and answers in the use of Go framework

In the development of Go framework, we often encounter some confusing problems question. This article explores these common problems and their solutions, including real-life examples.

1. "__createDatabase__ is not a function" error occurs when connecting to the database

func init() {
    _, err := db.CreateDatabase("my_db")
    if err != nil {
        log.Fatal(err)
    }
}

Solution:

Use# The ##Create method replaces the CreateDatabase method. CreateDatabase is only provided by the underlying driver and does not work with all databases.

2. "bad request: field required" error occurs when a specific field in the model is set to null

type User struct {
    ID        int    `gorm:"primary_key"`
    Email     string `gorm:"unique_index"`
    Name      *string
    CreatedAt time.Time
    UpdatedAt time.Time
}

Solution:

Ensure that

null fields are nullable. For string fields, use the string type instead of the *string type. For time fields, use the *time.Time type.

3. Unable to get the ID of a specific model row

var user User
db.First(&user, "name = ?", "John")
fmt.Println(user.ID) // 输出为 0

Solution:

Use

First or Last method, you need to ensure that the model structure has a primary key field, otherwise it will return a model containing zero values.

4. "tx has been committed or rolled back" error occurs when using transactions

func CreateUser(user *User) error {
    tx := db.Begin()
    defer tx.Rollback() // 假设失败后回滚

    if err := tx.Create(user).Error; err != nil {
        return err
    }

    if err := tx.Commit().Error; err != nil {
        return err
    }

    return nil
}

Solution:

Ensure that no errors occurred during transaction processing. If it fails, roll back the transaction immediately to prevent inconsistencies. If the transaction completes successfully, commit it before exiting.

5. The httprouter route handler cannot access the request's context string

func MyHandler(w http.ResponseWriter, r *http.Request) {
    fmt.Fprintf(w, "Context value: %s", r.Context().Value("key")) // 输出为空
}

Solution:

By using

httprouter.ParamsFromContext Function gets the context string of the request.

func MyHandler(w http.ResponseWriter, r *http.Request, ps httprouter.Params) {
    fmt.Fprintf(w, "Context value: %s", ps.ByName("key"))
}

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