Passing an CSVExport function to a handler Gin - go

Question

I have created a CSV export function for my to-do list application. The function is working, the handler is returning a written file but I get a strange panic in the console from the Gin framework:
http: wrote more than the declared Content-Length
Is that something crucial and how can I fix this panic.
This is my function:
func (r *Repository) CSVExport() (*os.File, error) {
tasks, err := r.getAllTasks()
if err != nil {
return nil, err
}
file, err := os.Create("tasks.csv")
if err != nil {
return nil, err
}
defer file.Close()
writer := csv.NewWriter(file)
defer writer.Flush()
var taskNameList []string
for _, task := range tasks {
taskNameList = append(taskNameList, task.Text)
}
err = writer.Write(taskNameList)
if err != nil {
return nil, err
}
return file, nil
}
And this is the handler:
func CSVExport(data model.ListOperations) gin.HandlerFunc {
return func(c *gin.Context) {
tasks, err := data.CSVExport()
if err != nil {
c.JSON(http.StatusBadRequest, gin.H{"error": "Invalid Task"})
}
c.FileAttachment("./tasks.csv", "tasks.csv")
c.Writer.Header().Set("attachment", "filename=tasks.csv")
c.JSON(200, tasks)
}
}

Answer 1

Your code has some error:
You need to return on error
You can't return JSON after returning your file with fileAttachment (it already does this stuff)
func CSVExport(data model.ListOperations) gin.HandlerFunc {
return func(c *gin.Context) {
tasks, err := data.CSVExport()
if err != nil {
c.JSON(http.StatusBadRequest, gin.H{"error": "Invalid Task"})
return //stop it on error
}
c.FileAttachment("./tasks.csv", "tasks.csv")
c.Writer.Header().Set("attachment", "filename=tasks.csv")
//c.JSON(200, tasks) not need the fileAttachement func do it
}
}