我接下来使用 article将 Golang 应用程序与远程 Oracle 数据库连接起来。应用程序在库的帮助下成功连接到数据库 goracle .我也ping通了。当我进行 sql 查询时，应用程序引发错误。哪里错了？

我注意到，如果从 Controller 文件 (organizations.go) 中删除所有代码到连接文件 (Oracle.go)，它会起作用。我究竟需要如何重构？

错误:

2019/03/13 18:15:47 http: panic serving [::1]:28363: runtime error: invalid memory address or nil pointer dereference 
goroutine 54 [running]: 
net/http.(*conn).serve.func1(0xc0000dee60) 
    C:/Go/src/net/http/server.go:1746 +0xd7 
panic(0x874bc0, 0x7ff060) 
    C:/Go/src/runtime/panic.go:513 +0x1c7 
database/sql.(*DB).conn(0x0, 0x95d140, 0xc0000120a8, 0x1, 0x0, 0xc0000dec60, 0xc00037d950) 
    C:/Go/src/database/sql/sql.go:1081 +0x41 
database/sql.(*DB).query(0x0, 0x95d140, 0xc0000120a8, 0x8fde32, 0x65, 0x0, 0x0, 0x0, 0x6b2801, 0x8, ...) 
    C:/Go/src/database/sql/sql.go:1514 +0x6d 
database/sql.(*DB).QueryContext(0x0, 0x95d140, 0xc0000120a8, 0x8fde32, 0x65, 0x0, 0x0, 0x0, 0x30, 0x30, ...) 
    C:/Go/src/database/sql/sql.go:1496 +0xda 
database/sql.(*DB).Query(0x0, 0x8fde32, 0x65, 0x0, 0x0, 0x0, 0x78, 0x80, 0xc000446100) 
    C:/Go/src/database/sql/sql.go:1510 +0x89 
questionnaire/controllers.glob..func11(0x95cd80, 0xc000448000, 0xc00016e400) 
    C:/Users/NNogerbek/go/src/questionnaire/controllers/organizations.go:18 +0x6f 
net/http.HandlerFunc.ServeHTTP(0x9031f8, 0x95cd80, 0xc000448000, 0xc00016e400) 
    C:/Go/src/net/http/server.go:1964 +0x4b 
github.com/gorilla/mux.(*Router).ServeHTTP(0xc0003da300, 0x95cd80, 0xc000448000, 0xc000444000) 
    C:/Users/NNogerbek/go/src/github.com/gorilla/mux/mux.go:212 +0xd7 
github.com/gorilla/handlers.(*cors).ServeHTTP(0xc0000d8900, 0x95cd80, 0xc000448000, 0xc000444000) 
    C:/Users/NNogerbek/go/src/github.com/gorilla/handlers/cors.go:54 +0xa95 
net/http.serverHandler.ServeHTTP(0xc000054b60, 0x95cd80, 0xc000448000, 0xc000444000) 
    C:/Go/src/net/http/server.go:2741 +0xb2 
net/http.(*conn).serve(0xc0000dee60, 0x95d100, 0xc000178000) 
    C:/Go/src/net/http/server.go:1847 +0x64d 
created by net/http.(*Server).Serve 
    C:/Go/src/net/http/server.go:2851 +0x2fc 

结构:

- database 
    Oracle.go 
- routes 
    routes.go 
- controllers 
    organizations.go 
main.go 

ma​​in.go:

import ( 
    "github.com/gorilla/handlers" 
    "github.com/gorilla/mux" 
    "github.com/joho/godotenv" 
    "log" 
    "net/http" 
    "project/database" 
    "project/routes" 
    "project/utils" 
) 
 
func main()  { 
    err := godotenv.Load(".env") 
    if err != nil { 
        panic(err) 
    } 
 
    database.ConnectOracle() 
    defer database.DisconnectOracle() 
 
    router := mux.NewRouter() 
 
    headers := handlers.AllowedHeaders([]string{"X-Requested-With", "Content-Type", "Authorization"}) 
    methods := handlers.AllowedMethods([]string{"GET", "POST", "PATCH", "PUT", "DELETE", "OPTIONS"}) 
    origins := handlers.AllowedOrigins([]string{"*"}) 
 
    router.StrictSlash(true) 
 
    routes.Handle(router) 
 
    port := utils.CheckEnvironmentVariable("APPLICATION_PORT") 
 
    log.Printf("RESTful web service is running on %s port.", port) 
 
    log.Fatal(http.ListenAndServe(":" + port, handlers.CORS(headers, methods, origins)(router))) 
} 

Oracle.go:

package database 
 
import ( 
    "database/sql" 
    "fmt" 
    "github.com/joho/godotenv" 
    _ "gopkg.in/goracle.v2" 
    "log" 
    "questionnaire/utils" 
) 
 
var OracleDB *sql.DB 
 
func ConnectOracle() { 
    err := godotenv.Load(".env") 
    if err != nil { 
        log.Println(err) 
        panic(err) 
    } 
 
    databaseUser := utils.CheckEnvironmentVariable("ORACLE_USER") 
    databasePassword := utils.CheckEnvironmentVariable("ORACLE_PASSWORD") 
    databaseHost := utils.CheckEnvironmentVariable("ORACLE_HOST") 
    databasePort := utils.CheckEnvironmentVariable("ORACLE_PORT") 
    databaseName := utils.CheckEnvironmentVariable("ORACLE_DATABASE_NAME") 
 
    databaseURL:= fmt.Sprintf("%s/%s@%s:%s/%s", databaseUser, databasePassword, databaseHost, databasePort, databaseName) 
 
    OracleDB, err := sql.Open("goracle", databaseURL) 
    if err != nil { 
        log.Println(err) 
        panic(err) 
    } 
 
    err = OracleDB.Ping() 
    if err != nil { 
        log.Println(err) 
        panic(err) 
    } 
 
    log.Println("RESTful web service successfully connected to remote ORACLE database with the help of \"database/sql\" package.") 
} 
 
func DisconnectOracle() error { 
    return OracleDB.Close() 
} 

routes.go:

package routes 
 
import ( 
    "github.com/gorilla/mux" 
    "project/controllers" 
) 
 
func Handle(router *mux.Router) { 
    router.HandleFunc("/api/organizations", controllers.GetOrganizations).Methods("GET") 
} 

organizations.go:

package controllers 
 
import ( 
    "log" 
    "net/http" 
    "project/database" 
    "project/utils" 
) 
 
type Organisation struct { 
    OrganizationID int `json:"organization_id"` 
    ParentOrganizationID int `json:"parent_organization_id"` 
    OrganizationName string `json:"organization_name"` 
    OrganizationRang int `json:"organization_name"` 
} 
 
var GetOrganizations = func(responseWriter http.ResponseWriter, request *http.Request) { 
    rows, err := database.OracleDB.Query("SELECT ORGANIZATION_ID, PARENT_ORGANIZATION_ID, ORGANIZATION_NAME, ORGANIZATION_RANG FROM ORG_STR") 
    if err != nil { 
        log.Println(err) 
        utils.ResponseWithError(responseWriter, http.StatusInternalServerError, err.Error()) 
        return 
    } 
    defer rows.Close() 
 
    var organizations []Organisation 
 
    for rows.Next() { 
        var organization Organisation 
 
        if err := rows.Scan(&organization.OrganizationID, &organization.ParentOrganizationID, &organization.OrganizationName, &organization.OrganizationRang); err != nil { 
            log.Println(err) 
            utils.ResponseWithError(responseWriter, http.StatusInternalServerError, err.Error()) 
            return 
        } 
 
        organizations = append(organizations, organization) 
    } 
 
    utils.Response(responseWriter, http.StatusOK, organizations) 
} 

请您参考如下方法:

建议@mkopriva 的解决方案:

Change OracleDB, err := sql.Open("goracle", databaseURL) to OracleDB, err = sql.Open("goracle", databaseURL), and search for "go shadowing variables". To explain, your global OracleDB is never set because you use := in the local scope to "assign" it, but := declares and initializes a new variable named OracleDB that shadows the global one.