"Unable to start NATS Server in Go Routine" while testing

I'm trying to separate tests to use different NATS servers. (I'm not yet sure it is NATS, but my tests influence each other.)

Doing that works fine when running a single test or testing a single package. Running go test ./... on all my packages (as done in CI) I get this error (paths anonymised):

panic: Unable to start NATS Server in Go Routine

goroutine 1 [running]:
github.com/nats-io/gnatsd/test.RunServer(0xc000163400, 0xc000163400)
    ./go/pkg/mod/github.com/nats-io/gnatsd@v1.4.1/test/test.go:66 +0xbd
./lib/msgQueue/nats.NewTestConn(0xc0002adf68, 0x1879e12)
    ./lib/msgQueue/nats/testconn.go:19 +0x80

It seems like Go starts goroutines to run tests in them. Both using TestMain and init in the tests does not solve the problem.

Is it possible to start a server per test without running into the goroutine error? Or is there some lightweight, but functioning in-memory replacement?

---

Here some code:

// +build !build

package myNats

import (
    "fmt"

    "github.com/pkg/errors"
    "github.com/nats-io/gnatsd/server"
    "github.com/nats-io/gnatsd/test"
)

func NewTestConn() (conn *Conn, shutdown func()) {
    opts := server.Options{
        Host:   "localhost",
        Port:   53347,
        NoLog:  true,
        NoSigs: true,
    }
    gnatsd := test.RunServer(&opts)
    if gnatsd == nil {
        panic("could not start NATS test server")
    }

    url := fmt.Sprintf("nats://%s:%d", opts.Host, opts.Port)
    conn, err := open(url)
    if err != nil {
        panic(errors.Wrap(err, "could not connect to test NATS"))
    }

    return conn, func() {
        conn.close()
        gnatsd.Shutdown()
    }
}

My goal would be to have a server per test:

func TestSomeThing(t *testing.T) {
    conn, shutdown := myNats.NewTestConn()
    defer shutdown()

    _ = conn
    // test code here
}