Nil pointer panic trying to retrieve value from a map[string]struct{}

[mikimartin88 (Miki)]

Hi !

I’m receiving a runtime error: invalid memory address or nil pointer dereference accessing to a nil map:

var orgsToSendToPrometheus map[string]struct{}

func MustRegisterOverheadByOrg(org string) bool {
	if _, ok := orgsToSendToPrometheus[allOrgs]; ok {
		return true
	}
	_, ok := orgsToSendToPrometheus[org]
	return ok
}

That panics in line → _, ok := orgsToSendToPrometheus[org]

As I understand, read , delete, length, and range loops, are safe to perform on a nil map since it behaves like an empty map.

Could anyone help me?

Thanks!
Miki

[lemarkar (Leo Emar-Kar)]

Hello there. Can you provide error trace? And can you also specify where org comes from? For now, I don’t see any problems with accessing nil map: playground

[Yamil_Bracho]

I am not sure if the problem is with “allOrgs” key…

[lemarkar (Leo Emar-Kar)]

You told it panics with org key

[freeformz (Edward Muller)]

Go Playground - The Go Programming Language

See also: The Go Programming Language Specification - The Go Programming Language

“The value of an uninitialized map is nil.”
…
" A new, empty map value is made using the built-in function make, which takes the map type and …"

[mikimartin88 (Miki)]

Hi all!

Thank you for your responses.

org parameter is a string and could not be nil. Zero value is empty string. It always have a value != “” because I check it before calling MustRegisterOverheadByOrg.

allOrgs parameter is a string too with “all” value initialized at package level.

Here you have all code in the file

The error trace:

gitlab.xmltravelgate.com/hub-aggregator/kit/log.(*Logger).Error
/go/pkg/mod/gitlab.xmltravelgate.com/hub-aggregator/kit@v1.46.22/log/logger.go:68
gitlab.xmltravelgate.com/hub-aggregator/booking/common/kit/audit.Middleware.func1.1.1
/go/src/bf/booking/common/kit/audit/audit.go:119
runtime.gopanic
/usr/local/go/src/runtime/panic.go:884
runtime.panicmem
/usr/local/go/src/runtime/panic.go:260
runtime.sigpanic
/usr/local/go/src/runtime/signal_unix.go:841
memeqbody
/usr/local/go/src/internal/bytealg/equal_amd64.s:151
runtime.mapaccess2_faststr
/usr/local/go/src/runtime/map_faststr.go:133
gitlab.xmltravelgate.com/hub-aggregator/booking/common/connectx/hardCode.MustRegisterOverheadByOrg
/go/src/bf/booking/common/connectx/hardCode/operation_sla.go:30
gitlab.xmltravelgate.com/hub-aggregator/booking/pkg/flow/bfhttp.RegisterSLAStats
/go/src/bf/booking/pkg/flow/bfhttp/metric.go:178
gitlab.xmltravelgate.com/hub-aggregator/kit/http.(*Handler).ServeHTTP
/go/pkg/mod/gitlab.xmltravelgate.com/hub-aggregator/kit@v1.46.22/http/handler.go:90
gitlab.xmltravelgate.com/hub-aggregator/booking/common/connectx.TransactionMiddleware.func1.1
/go/src/bf/booking/common/connectx/transaction.go:124
net/http.HandlerFunc.ServeHTTP
/usr/local/go/src/net/http/server.go:2122
github.com/travelgateX/go-jwt-tools.Middleware.func1.1
/go/pkg/mod/github.com/travelgate!x/go-jwt-tools@v1.5.0/auth.go:42
net/http.HandlerFunc.ServeHTTP
/usr/local/go/src/net/http/server.go:2122
gitlab.xmltravelgate.com/hub-aggregator/tgx-kit/header.Middleware.func1.1
/go/pkg/mod/gitlab.xmltravelgate.com/hub-aggregator/tgx-kit@v1.77.68/header/header.go:235
net/http.HandlerFunc.ServeHTTP
/usr/local/go/src/net/http/server.go:2122
gitlab.xmltravelgate.com/hub-aggregator/booking/common/kit/audit.Middleware.func1.1
/go/src/bf/booking/common/kit/audit/audit.go:165
net/http.HandlerFunc.ServeHTTP
/usr/local/go/src/net/http/server.go:2122
github.com/gorilla/handlers.CompressHandlerLevel.func1
/go/pkg/mod/github.com/gorilla/handlers@v1.5.1/compress.go:141
net/http.HandlerFunc.ServeHTTP
/usr/local/go/src/net/http/server.go:2122
gitlab.xmltravelgate.com/hub-aggregator/booking/common/stats.Middleware.func1.1
/go/src/bf/booking/common/stats/stats.go:209
net/http.HandlerFunc.ServeHTTP
/usr/local/go/src/net/http/server.go:2122
github.com/gorilla/handlers.(*cors).ServeHTTP
/go/pkg/mod/github.com/gorilla/handlers@v1.5.1/cors.go:54
gitlab.xmltravelgate.com/hub-aggregator/kit/http.Duplicate.func1.1
/go/pkg/mod/gitlab.xmltravelgate.com/hub-aggregator/kit@v1.46.22/http/duplicate.go:206
net/http.HandlerFunc.ServeHTTP
/usr/local/go/src/net/http/server.go:2122
github.com/gorilla/mux.(*Router).ServeHTTP
/go/pkg/mod/github.com/gorilla/mux@v1.8.0/mux.go:210
net/http.serverHandler.ServeHTTP
/usr/local/go/src/net/http/server.go:2936
net/http.(*conn).serve
/usr/local/go/src/net/http/server.go:1995

Thank you!

[lemarkar (Leo Emar-Kar)]

Yeah and specs also state:

A nil map is equivalent to an empty map except that no elements may be added.