```go
package main
import (
"database/sql"
"github.com/gin-gonic/gin"
_ "github.com/go-sql-driver/mysql"
"log"
"net/http"
)
type Person struct {
Id int `json:"id" from:"id"`
FirstName string `json:"first_name" form:"first_name"`
LastName string `json:"last_name" form:"last_name"`
}
func init() {
db, err := sql.Open("mysql", "root:123456@tcp(127.0.0.1)/test_go?parseTime=true")
if err != nil {
log.Fatalln(err)
}
defer db.Close()
db.SetMaxIdleConns(20)
db.SetMaxOpenConns(20)
if err := db.Ping(); err != nil {
log.Fatalln(err)
}
}
var db sql.DB
func main() {
router := gin.Default()
router.GET("/", func(c *gin.Context) {
c.String(http.StatusOK, "It works")
})
router.GET("/persons/:id", getPersonApi)
router.Run("127.0.0.1:8000")
}
func getPersonApi(c *gin.Context) {
id := c.Param("id")
var person Person
// 出错地方---------------
err := db.QueryRow("select id,first_name,last_name from person where id=?", id).Scan(&person.Id, &person.FirstName, &person.LastName)
if err != nil {
log.Fatalln(err)
c.JSON(http.StatusOK, gin.H{
"person": nil,
})
return
}
c.JSON(http.StatusOK, gin.H{
"person": person,
})
}
```
///////////////////////////////////////////////////////报错信息/////////////////////////////////////////////////////////////////////////
```
2019/02/22 00:25:03 [Recovery] 2019/02/22 - 00:25:03 panic recovered:
GET /persons/1 HTTP/1.1
Host: localhost:8000
Accept: */*
Accept-Encoding: gzip, deflate
Authorization: eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJleHAiOiIxNTUwOTMxMjA5MDY3Njk2MDAwIiwiaWF0IjoxNTUwNjcyMDA5LCJqdGkiOiJ0b2tlbiJ9.r0a4g5nUr8cttYvuQOSOrVOiuOCObvS-fOE23YK8SQM
Cache-Control: no-cache
Connection: keep-alive
Content-Length: 34
Content-Type: application/json
Cookie: shiro.session=ca6b90a7-5772-49ff-9318-c6367be17494
Postman-Token: 242be282-0dd9-4718-8fbb-23ac504f78c1
User-Agent: PostmanRuntime/7.6.0
runtime error: invalid memory address or nil pointer dereference
/usr/local/Cellar/go/1.11.5/libexec/src/runtime/panic.go:513 (0x102bdc8)
gopanic: reflectcall(nil, unsafe.Pointer(d.fn), deferArgs(d), uint32(d.siz), uint32(d.siz))
/usr/local/Cellar/go/1.11.5/libexec/src/runtime/panic.go:82 (0x102af1d)
panicmem: panic(memoryError)
/usr/local/Cellar/go/1.11.5/libexec/src/runtime/signal_unix.go:390 (0x10412e1)
sigpanic: panicmem()
/usr/local/Cellar/go/1.11.5/libexec/src/database/sql/sql.go:1177 (0x10e0741)
(*DB).conn: ci, err := db.connector.Connect(ctx)
/usr/local/Cellar/go/1.11.5/libexec/src/database/sql/sql.go:1514 (0x10e3265)
(*DB).query: dc, err := db.conn(ctx, strategy)
/usr/local/Cellar/go/1.11.5/libexec/src/database/sql/sql.go:1496 (0x10e2f92)
(*DB).QueryContext: rows, err = db.query(ctx, query, args, cachedOrNewConn)
/usr/local/Cellar/go/1.11.5/libexec/src/database/sql/sql.go:1597 (0x10e3c8c)
(*DB).QueryRowContext: rows, err := db.QueryContext(ctx, query, args...)
/usr/local/Cellar/go/1.11.5/libexec/src/database/sql/sql.go:1608 (0x10e3dbb)
(*DB).QueryRow: return db.QueryRowContext(context.Background(), query, args...)
/Users/walker/go/src/gin/test.go:47 (0x159c880)
getPersonApi: err := db.QueryRow("select id,first_name,last_name from person where id=?", id).Scan(&person.Id, &person.FirstName, &person.LastName)
/Users/walker/go/src/github.com/gin-gonic/gin/context.go:109 (0x1569ee9)
(*Context).Next: c.handlers[c.index](c)
/Users/walker/go/src/github.com/gin-gonic/gin/recovery.go:76 (0x157c8b9)
RecoveryWithWriter.func1: c.Next()
/Users/walker/go/src/github.com/gin-gonic/gin/context.go:109 (0x1569ee9)
(*Context).Next: c.handlers[c.index](c)
/Users/walker/go/src/github.com/gin-gonic/gin/logger.go:176 (0x157bc40)
LoggerWithConfig.func1: c.Next()
/Users/walker/go/src/github.com/gin-gonic/gin/context.go:109 (0x1569ee9)
(*Context).Next: c.handlers[c.index](c)
/Users/walker/go/src/github.com/gin-gonic/gin/gin.go:386 (0x157344a)
(*Engine).handleHTTPRequest: c.Next()
/Users/walker/go/src/github.com/gin-gonic/gin/gin.go:349 (0x1572c91)
(*Engine).ServeHTTP: engine.handleHTTPRequest(c)
/usr/local/Cellar/go/1.11.5/libexec/src/net/http/server.go:2741 (0x129a27a)
serverHandler.ServeHTTP: handler.ServeHTTP(rw, req)
/usr/local/Cellar/go/1.11.5/libexec/src/net/http/server.go:1847 (0x12964c5)
(*conn).serve: serverHandler{c.server}.ServeHTTP(w, w.req)
/usr/local/Cellar/go/1.11.5/libexec/src/runtime/asm_amd64.s:1333 (0x1058fc0)
goexit: BYTE $0x90 // NOP
[GIN] 2019/02/22 - 00:25:03 | 500 | 3.181345ms | 127.0.0.1 | GET /persons/1
```
有疑问加站长微信联系（非本文作者））
