Can't connect Azure Postgresql and error received unexpected message

Nobody has claimed this yet.

I don't know why 'received unexpected message' or your not suppport azure?
```
package main

import (
"context"
"fmt"
"os"

"github.com/jackc/pgx/v4"
)

func main() {
conn, err := pgx.Connect(context.Background(), "postgresql://xxxxx@cg-x-x-nonprd:xxxxxxxx@cg-x-x-nonprd.postgres.database.azure.com:5432/abcd?sslmode=require")
if err != nil {
fmt.Fprintf(os.Stderr, "Unable to connect to database: %v\n", err)
os.Exit(1)
}
defer conn.Close(context.Background())

var greeting string
err = conn.QueryRow(context.Background(), "select 'Hello, world!'").Scan(&greeting)
if err != nil {
fmt.Fprintf(os.Stderr, "QueryRow failed: %v\n", err)
os.Exit(1)
}

fmt.Println(greeting)
}
```

```
λ go run pgx.go
Unable to connect to database: failed to connect to `host=cg-x-x-nonprd.postgres.database.azure.com user=xxxxx@cg-x-x-nonprd database=abcd`: received unexpected message
exit status 1
```

Ref version
`go 1.16.4`
`windows 10`
`Azure Postgresql 11`

Start with the pgx.go reproduction and the pgx.Connect call, using the supplied Azure PostgreSQL 11 connection details and error output. Confirm whether the failure is specific to Azure or the connection configuration, and document a verified diagnosis or a minimal reproducible case as done.

Written by the indexing model from the issue text.