<分区>
我是 Go 的新手，需要帮助!
在 PostgreSQL 数据库中，我有一个名为 factors 的表。该表有 2 列(factor_id 和 factor_name)。现在，我已从 Go 应用程序成功连接到 PostgreSQL 数据库。
当我试图在控制台中发出基于查询的 GET 请求时，我看到了错误。
http://localhost:8000/api/factors/?limit=5&offset=1
我哪里弄错了？请帮助我解决问题。
controllers/factors.go:
package controllers
import (
"encoding/json"
"fmt"
"net/http"
"restify/models"
"restify/utils"
)
var GetFactors = func(res http.ResponseWriter, req *http.Request) {
data := models.Factors{}
err := models.GetFactors(&data, req.URL.Query().Get("limit"), req.URL.Query().Get("offset"))
if err != nil {
fmt.Println(err.Error())
http.Error(res, err.Error(), 500)
return
}
out, err := json.Marshal(data)
if err != nil {
fmt.Println(err.Error())
http.Error(res, err.Error(), 501)
return
}
resp := make(map[string]interface{})
resp["Dictionaries"] = string(out)
utils.Respond(res, resp)
}
models/factors.go:
package models
import (
"fmt"
"restify/database"
)
type Factor struct {
FactorID int `json:"factor_id"`
FactorName string `json:"factor_name"`
}
type Factors struct {
Array[]Factor
}
func GetFactors(data *Factors, limit string, offset string) error {
rows, err := database.DB.Query(`SELECT * FROM factors ORDER BY factor_id LIMIT ` + limit + ` OFFSET ` + offset + `;`)
if err != nil {
fmt.Println(err)
return err
}
defer rows.Close()
for rows.Next() {
var id int
var name string
model := Factor{}
err = rows.Scan(&id, &name)
if err != nil {
fmt.Println(err)
return err
}
model.FactorID = id
model.FactorName = name
data.Array = append(data.Array, model)
}
err = rows.Err()
if err != nil {
return err
}
return nil
}
错误:
2019/02/26 16:25:55 http: panic serving [::1]:20932: runtime error: invalid memory address or nil pointer dereference
goroutine 11 [running]:
net/http.(*conn).serve.func1(0xc0002badc0)
C:/Go/src/net/http/server.go:1746 +0xd7
panic(0x6dad20, 0x970890)
C:/Go/src/runtime/panic.go:513 +0x1c7
database/sql.(*DB).conn(0x0, 0x78a500, 0xc0000100a8, 0x10000c000339801, 0x0, 0xc000339898, 0xc000339830)
C:/Go/src/database/sql/sql.go:1081 +0x41
database/sql.(*DB).query(0x0, 0x78a500, 0xc0000100a8, 0xc000356040, 0x3a, 0x0, 0x0, 0x0, 0xc000356001, 0x3a, ...)
C:/Go/src/database/sql/sql.go:1514 +0x6d
database/sql.(*DB).QueryContext(0x0, 0x78a500, 0xc0000100a8, 0xc000356040, 0x3a, 0x0, 0x0, 0x0, 0x5, 0xc000356040, ...)
C:/Go/src/database/sql/sql.go:1496 +0xda
database/sql.(*DB).Query(0x0, 0xc000356040, 0x3a, 0x0, 0x0, 0x0, 0x8, 0xc00034e016, 0x1)
C:/Go/src/database/sql/sql.go:1510 +0x89
restify/models.GetFactors(0xc000339b28, 0xc00034e016, 0x1, 0xc00034e01e, 0x1, 0x0, 0x0)
C:/Users/NNogerbek/go/src/restify/models/factors.go:18 +0xf6
restify/controllers.glob..func1(0x78a2c0, 0xc00035a000, 0xc000332200)
C:/Users/NNogerbek/go/src/restify/controllers/factors.go:14 +0xd3
net/http.HandlerFunc.ServeHTTP(0x74da58, 0x78a2c0, 0xc00035a000, 0xc000332200)
C:/Go/src/net/http/server.go:1964 +0x4b
github.com/gorilla/mux.(*Router).ServeHTTP(0xc0002fc180, 0x78a2c0, 0xc00035a000, 0xc000310300)
C:/Users/NNogerbek/go/src/github.com/gorilla/mux/mux.go:212 +0xd7
github.com/gorilla/handlers.(*cors).ServeHTTP(0xc0001f2120, 0x78a2c0, 0xc00035a000, 0xc000310300)
C:/Users/NNogerbek/go/src/github.com/gorilla/handlers/cors.go:54 +0xa95
net/http.serverHandler.ServeHTTP(0xc000056b60, 0x78a2c0, 0xc00035a000, 0xc000310300)
C:/Go/src/net/http/server.go:2741 +0xb2
net/http.(*conn).serve(0xc0002badc0, 0x78a4c0, 0xc000340040)
C:/Go/src/net/http/server.go:1847 +0x64d
created by net/http.(*Server).Serve
C:/Go/src/net/http/server.go:2851 +0x2fc
database/database.go:
package database
import (
"database/sql"
"fmt"
"github.com/joho/godotenv"
_ "github.com/lib/pq"
"log"
"restify/utils"
)
var DB *sql.DB
/*
Function: "Connect".
Description:
The main task of the function is to initialize database connection.
*/
func Open() () {
// Load environment variables from ".env" file.
err := godotenv.Load(".env")
if err != nil {
panic(err)
}
// Initialize database related variables.
dbUser := utils.CheckEnvironmentVariable("PostgreSQL_USER")
dbPassword := utils.CheckEnvironmentVariable("PostgreSQL_PASSWORD")
dbHost := utils.CheckEnvironmentVariable("PostgreSQL_HOST")
dbName := utils.CheckEnvironmentVariable("PostgreSQL_DATABASE_NAME")
// Defining connection string for PostgreSQL database.
dbURL := fmt.Sprintf("user=%s password=%s host=%s dbname=%s sslmode=disable", dbUser, dbPassword, dbHost, dbName)
// Create PostgreSQL database connection pool.
DB, err := sql.Open("postgres", dbURL)
if err != nil {
panic(err)
}
// Ping PostgreSQL database to make sure it's alive.
err = DB.Ping()
if err != nil {
panic(err)
}
log.Println("REST API web service successfully connected to remote PostgreSQL database.")
}
/*
Function: "Disconnect"
Description:
The main task of the function is to disconnect database connection.
*/
func Close() error {
return DB.Close()
}