Error when using gqlapollotracing with subscriptions

Hi,

I've been using gqlapollotracing but lately when I started playing with subscriptions I realized the subscriptions only work when I don't use tracing, otherwise I get this error when I subscribe to a subscription and a value is sent through the chan:

interface conversion: interface {} is nil, not *gqlapollotracing.tracingData

goroutine 28 [running]:
runtime/debug.Stack(0x1, 0x0, 0x0)
        /usr/local/go/src/runtime/debug/stack.go:24 +0xa7
runtime/debug.PrintStack()
        /usr/local/go/src/runtime/debug/stack.go:16 +0x22
github.com/99designs/gqlgen/graphql.DefaultRecover(0x193f9a0, 0xc00042dcc0, 0x1783500, 0xc000b320f0, 0x203000, 0x203000)
        /Users/Username/golang/src/github.com/99designs/gqlgen/graphql/recovery.go:16 +0xa7
github.com/99designs/gqlgen/handler.(*wsConnection).subscribe.func1.1(0xc0000b70e0, 0x193f9a0, 0xc00042dcc0, 0xc000b1e2d0, 0xc00042d800)
        /Users/Username/golang/src/github.com/99designs/gqlgen/handler/websocket.go:223 +0x73
panic(0x1783500, 0xc000b320f0)
        /usr/local/go/src/runtime/panic.go:513 +0x1b9
github.com/99designs/gqlgen-contrib/gqlapollotracing.getTracingData(0x193fa60, 0xc000ad9ec0, 0xc000086800)
        /Users/Username/golang/src/github.com/99designs/gqlgen-contrib/gqlapollotracing/tracer.go:25 +0x88
github.com/99designs/gqlgen-contrib/gqlapollotracing.(*tracerImpl).StartFieldExecution(0x1f023d0, 0x193fa60, 0xc000ad9ec0, 0xc0000dcb80, 0x0, 0x0, 0x0, 0x0, 0x0)
        /Users/Username/golang/src/github.com/99designs/gqlgen-contrib/gqlapollotracing/tracer.go:67 +0x58
MY_APP/graphql/gql.(*executionContext)._Message_content(0xc000b60970, 0x193fa60, 0xc000ad9ec0, 0xc0000dcb80, 0x0, 0x0, 0x0, 0xc0000dcc80, 0x0, 0x0)
        /Users/Username/workspace/MY_APP_MONOREPO/golang/src/MY_APP/graphql/gql/generated_gen.go:6471 +0xde
MY_APP/graphql/gql.(*executionContext)._Message(0xc000b60970, 0x193fa60, 0xc000ad9ec0, 0xc0000fd040, 0x2, 0x2, 0xc0000dcc80, 0x1, 0xc000b32090)
        /Users/Username/workspace/MY_APP_MONOREPO/golang/src/MY_APP/graphql/gql/generated_gen.go:6380 +0x826
MY_APP/graphql/gql.(*executionContext)._Subscription_messageAdded.func1.1(0xc000b60970, 0x193fa60, 0xc000ad9ec0, 0xc0000dcb00, 0xc0000fd040, 0x2, 0x2, 0xc0000dcc80, 0x17d7c20, 0xc000067c01)
        /Users/Username/workspace/MY_APP_MONOREPO/golang/src/MY_APP/graphql/gql/generated_gen.go:11204 +0x74
MY_APP/graphql/gql.(*executionContext)._Subscription_messageAdded.func1(0xc00003ec30, 0x205cd80)
        /Users/Username/workspace/MY_APP_MONOREPO/golang/src/MY_APP/graphql/gql/generated_gen.go:11205 +0x17a
MY_APP/graphql/gql.(*executableSchema).Subscription.func1.1(0x193f9a0, 0xc00042dcc0, 0xc00042dcc0, 0x193f9a0, 0xc00042dcc0)
        /Users/Username/workspace/MY_APP_MONOREPO/golang/src/MY_APP/graphql/gql/generated_gen.go:2973 +0x47
github.com/99designs/gqlgen/handler.Tracer.func1.1(0x193f9a0, 0xc00042dcc0, 0xc0000fd0c0, 0xc0000fd0e0, 0x0, 0xc000b5e000)
        /Users/Username/golang/src/github.com/99designs/gqlgen/handler/graphql.go:168 +0x78
github.com/99designs/gqlgen/handler.RequestMiddleware.func1.1.1(0x193f9a0, 0xc00042dcc0, 0xc00000e168, 0x18, 0x18)
        /Users/Username/golang/src/github.com/99designs/gqlgen/handler/graphql.go:145 +0x42
github.com/99designs/gqlgen-contrib/gqlapollotracing.RequestMiddleware.func1(0x193f9a0, 0xc00042dcc0, 0xc0000fd0e0, 0x100e158,0x20, 0x17bd340)
        /Users/Username/golang/src/github.com/99designs/gqlgen-contrib/gqlapollotracing/middleware.go:11 +0x3e
github.com/99designs/gqlgen/handler.RequestMiddleware.func1.1(0x193f9a0, 0xc00042dcc0, 0xc0000fd0c0, 0xc000ad9e30, 0xc000b606b0, 0x1)
        /Users/Username/golang/src/github.com/99designs/gqlgen/handler/graphql.go:144 +0x8f
MY_APP/graphql/gql.(*executableSchema).Subscription.func1(0xc00047c000)
        /Users/Username/workspace/MY_APP_MONOREPO/golang/src/MY_APP/graphql/gql/generated_gen.go:2971 +0xb5
github.com/99designs/gqlgen/handler.(*wsConnection).subscribe.func1(0xc0000b70e0, 0x193f9a0, 0xc00042dcc0, 0xc000b1e2d0, 0xc00042d800, 0xc0000de2a0, 0xc000b60960)
        /Users/Username/golang/src/github.com/99designs/gqlgen/handler/websocket.go:228 +0xba
created by github.com/99designs/gqlgen/handler.(*wsConnection).subscribe
        /Users/Username/golang/src/github.com/99designs/gqlgen/handler/websocket.go:220 +0x52c

Here's where I use tracing :

gqlHandler := handler.GraphQL(
        // ...
        handler.RequestMiddleware(gqlapollotracing.RequestMiddleware()),
        handler.Tracer(gqlapollotracing.NewTracer()),
        // ...
    )

So for the moment I'm just gonna stop using it. I'll try digging into it If I have time.

Thanks for your work.

Similar error with gqlopencensus:

// ...
handler.Tracer(gql.NewMultiTracer(gqlopencensus.New(), gqllogger.New()))
// ...

Dump:

interface conversion: interface {} is nil, not time.Time

goroutine 28 [running]:
runtime/debug.Stack(0x1, 0x0, 0x0)
    /usr/local/Cellar/go/1.13/libexec/src/runtime/debug/stack.go:24 +0x9d
runtime/debug.PrintStack()
    /usr/local/Cellar/go/1.13/libexec/src/runtime/debug/stack.go:16 +0x22
github.com/99designs/gqlgen/graphql.DefaultRecover(0x21ea260, 0xc0004ba880, 0x1dd9760, 0xc0005ac510, 0x203000, 0x203000)
    /Users/leebenson/dev/omitted/vendor/github.com/99designs/gqlgen/graphql/recovery.go:16 +0xa7
github.com/99designs/gqlgen/handler.(*wsConnection).subscribe.func1.1(0xc00010a420, 0x21ea260, 0xc0004ba880, 0xc0005300c0, 0xc0004ba640)
    /Users/leebenson/dev/omitted/vendor/github.com/99designs/gqlgen/handler/websocket.go:258 +0x73
panic(0x1dd9760, 0xc0005ac510)
    /usr/local/Cellar/go/1.13/libexec/src/runtime/panic.go:679 +0x1b2
github.com/omitted/pkg/gqllogger.tracerImpl.EndOperationExecution(0x0, 0x21ea320, 0xc0005ac4e0)
    /Users/leebenson/dev/omitted/pkg/gqllogger/tracer.go:126 +0x3c9
github.com/omitted/pkg/gql.multitracerImpl.EndOperationExecution(0xc0004546a0, 0x2, 0x2, 0x21ea320, 0xc0005ac4e0)
    /Users/leebenson/dev/omitted/pkg/gql/multitracer.go:88 +0x6e
github.com/99designs/gqlgen/handler.Tracer.func1.1(0x21ea320, 0xc0005ac4e0, 0xc00059afa0, 0x1e95ca0, 0xc0005ac450, 0xc0004ba880)
    /Users/leebenson/dev/omitted/vendor/github.com/99designs/gqlgen/handler/graphql.go:202 +0xbe
github.com/omitted/pkg/gql.(*executableSchema).Subscription.func1(0xc0001c0a00)
    /Users/leebenson/dev/omitted/pkg/gql/exec.go:6519 +0xb5
github.com/99designs/gqlgen/handler.(*wsConnection).subscribe.func1(0xc00010a420, 0x21ea260, 0xc0004ba880, 0xc0005300c0, 0xc0004ba640, 0xc000375ce0, 0xc00046b1f0)
    /Users/leebenson/dev/omitted/vendor/github.com/99designs/gqlgen/handler/websocket.go:263 +0xed
created by github.com/99designs/gqlgen/handler.(*wsConnection).subscribe
    /Users/leebenson/dev/omitted/vendor/github.com/99designs/gqlgen/handler/websocket.go:255 +0x680

99designs / gqlgen-contrib

Error when using gqlapollotracing with subscriptions #10