Integrating Qor with Beego, getting invalid memory address or nil pointer dereference error

I have a simple web app that is using the Beego framework. I have recently discovered and want to play around with using it along side Beego.

I have followed this documentation to integrate Qor with my Beego web app.

When deploying, everything goes smoothly. The container builds and runs just fine and the original parts of my web app all work as expected. However, I get the following error when attempting to access the /admin page:

beego-app:runtime error: invalid memory address or nil pointer dereference
Request Method:	GET
Request URL:	/admin
RemoteAddr:	REDACTED
Stack
/usr/local/go/src/runtime/panic.go:838
/usr/local/go/src/runtime/panic.go:220
/usr/local/go/src/runtime/signal_unix.go:818
/usr/local/go/src/html/template/template.go:97
/usr/local/go/src/html/template/template.go:121
/go/pkg/mod/github.com/qor/admin@v1.2.0/context.go:227
/go/pkg/mod/github.com/qor/admin@v1.2.0/controller.go:28
/go/pkg/mod/github.com/qor/admin@v1.2.0/route.go:197
/go/pkg/mod/github.com/qor/admin@v1.2.0/route.go:38
/go/pkg/mod/github.com/qor/admin@v1.2.0/route.go:187
/go/pkg/mod/github.com/qor/admin@v1.2.0/route.go:38
/go/pkg/mod/github.com/qor/admin@v1.2.0/composite_primary_key_callback.go:27
/go/pkg/mod/github.com/qor/admin@v1.2.0/route.go:288
/usr/local/go/src/net/http/server.go:2462
/go/pkg/mod/github.com/astaxie/beego@v1.12.3/router.go:820
/usr/local/go/src/net/http/server.go:2916
/usr/local/go/src/net/http/server.go:1966
/usr/local/go/src/runtime/asm_amd64.s:1571
beego 1.12.3 (beego framework)

golang version: go1.18.3

Here is the logs I get from GCP:

Default
2022-07-21T20:18:54.881125Z2022/07/21 20:18:54.881 [1;35m[C][0m [panic.go:838] /go/pkg/mod/github.com/qor/admin@v1.2.0/controller.go:28
Default
2022-07-21T20:18:54.881131Z2022/07/21 20:18:54.881 [1;35m[C][0m [panic.go:838] /go/pkg/mod/github.com/qor/admin@v1.2.0/route.go:197
Default
2022-07-21T20:18:54.881138Z2022/07/21 20:18:54.881 [1;35m[C][0m [panic.go:838] /go/pkg/mod/github.com/qor/admin@v1.2.0/route.go:38
Default
2022-07-21T20:18:54.881144Z2022/07/21 20:18:54.881 [1;35m[C][0m [panic.go:838] /go/pkg/mod/github.com/qor/admin@v1.2.0/route.go:187
Default
2022-07-21T20:18:54.881152Z2022/07/21 20:18:54.881 [1;35m[C][0m [panic.go:838] /go/pkg/mod/github.com/qor/admin@v1.2.0/route.go:38
Default
2022-07-21T20:18:54.881161Z2022/07/21 20:18:54.881 [1;35m[C][0m [panic.go:838] /go/pkg/mod/github.com/qor/admin@v1.2.0/composite_primary_key_callback.go:27
Default
2022-07-21T20:18:54.881168Z2022/07/21 20:18:54.881 [1;35m[C][0m [panic.go:838] /go/pkg/mod/github.com/qor/admin@v1.2.0/route.go:288
Default
2022-07-21T20:18:54.881174Z2022/07/21 20:18:54.881 [1;35m[C][0m [panic.go:838] /usr/local/go/src/net/http/server.go:2462
Default
2022-07-21T20:18:54.881181Z2022/07/21 20:18:54.881 [1;35m[C][0m [panic.go:838] /go/pkg/mod/github.com/astaxie/beego@v1.12.3/router.go:820
Default
2022-07-21T20:18:54.881248Z2022/07/21 20:18:54.881 [1;35m[C][0m [panic.go:838] /usr/local/go/src/net/http/server.go:2916
Default
2022-07-21T20:18:54.881336Z2022/07/21 20:18:54.881 [1;35m[C][0m [panic.go:838] /usr/local/go/src/net/http/server.go:1966
Default
2022-07-21T20:18:54.881346Z2022/07/21 20:18:54.881 [1;35m[C][0m [panic.go:838] /usr/local/go/src/runtime/asm_amd64.s:1571
Default
2022-07-21T20:18:54.881475Z2022/07/21 20:18:54.881 [server.go:3195] [HTTP] http: superfluous response.WriteHeader call from github.com/astaxie/beego/context.(*Response).WriteHeader (context.go:230)
Info
2022-07-21T20:18:54.882870ZGET2002.99 KB2 msChrome 103 https://beego-app-epcfdn7vua-uc.a.run.app/admin

[server.go:3195] [HTTP] http: superfluous response.WriteHeader call from github.com/astaxie/beego/context.(*Response).WriteHeader (context.go:230)

From my searching, this has something to do with the header being written to more than once, but I am unable to locate the source of this.

main.go:

package main

import (
	_ "beego-app/routers"
	"net/http"

	"github.com/jinzhu/gorm"
	_ "github.com/jinzhu/gorm/dialects/sqlite"
	"github.com/qor/admin"

	web "github.com/astaxie/beego"
)

// Define a GORM-backend model
type User struct {
	gorm.Model
	Name string
}

// Define another GORM-backend model
type Product struct {
	gorm.Model
	Name        string
	Description string
}

func main() {
	// Set up the database
	database, _ := gorm.Open("sqlite3", "demo.db")
	database.AutoMigrate(&User{}, &Product{})

	// Initalize
	Admin := admin.New(&admin.AdminConfig{DB: database})

	// Create resources from GORM-backend model
	Admin.AddResource(&User{})
	Admin.AddResource(&Product{})

	// Mount admin to the mux
	newMux := http.NewServeMux()
	Admin.MountTo("/admin", newMux)
	web.Handler("/admin/*", newMux)
	web.Run()
}

Dockerfile:

FROM registry.semaphoreci.com/golang:1.18 as builder

ENV APP_HOME /go/src/beego-app

WORKDIR "$APP_HOME"
COPY / .

RUN go mod download
RUN go mod verify
RUN go build -o beego-app

FROM registry.semaphoreci.com/golang:1.18

ENV APP_HOME /go/src/beego-app
RUN mkdir -p "$APP_HOME"
WORKDIR "$APP_HOME"

COPY / .
COPY --from=builder "$APP_HOME"/beego-app $APP_HOME

EXPOSE 8080
CMD ["./beego-app"]

Any help would be greatly appreciated.

Solved this myself. I don't entirely understand why, but from what I can gather, Qor was not written using go modules and therefore it was throwing this error because the app couldn't locate the default template files.

The fix was simply to copy $GOPATH/pkg/mod/github.com/qor/qor/admin/views/ to $APP_DIR/app/views/qor/ so the application can access the template files.