Cannot find module for path github.com/influxdata/influxdb1-client/v2

Trying to build a go module (using go 1.11) with the InfluxDB client imported throws an error. Here is a snippet to reproduce this:

```
package main // import "github.com/user/influx"

import "github.com/influxdata/influxdb1-client/v2"

func main() {
// Do anything with the library
client.NewHTTPClient(client.HTTPConfig{})
}
```

Building without modules succeeds:
```
ak@zonda:/tmp/influx$ go build
ak@zonda:/tmp/influx$ ll
total 6404
drwxrwxr-x 2 ak ak 4096 Jan 24 19:59 ./
drwxrwxrwt 25 root root 16384 Jan 24 19:59 ../
-rwxrwxr-x 1 ak ak 6531840 Jan 24 19:59 influx*
-rw-rw-r-- 1 ak ak 191 Jan 24 19:56 main.go
```

Trying to build a module fails:
```
ak@zonda:/tmp/influx$ go mod init
go: creating new go.mod: module github.com/user/influx
ak@zonda:/tmp/influx$ go build
go: finding github.com/influxdata/influxdb1-client/v2 latest
go: downloading github.com/influxdata/influxdb1-client/v2 v2.0.0-20190118215656-f8cdb5d5f175
build github.com/user/influx: cannot find module for path github.com/influxdata/influxdb1-client/v2
```

Any tips? Thanks in advance!

Start by reproducing the failure with the Go 1.11 module commands and the import path shown in the issue. Compare the successful non-module build with the failing module build; done means the sample module can resolve the client package and build successfully.

Written by the indexing model from the issue text.