test.swift

#!/usr/bin/swift sh
import PostgreSQL  // https://github.com/vapor/postgresql.git ~> 1.0.0

let group = MultiThreadedEventLoopGroup(numberOfThreads: 1)

struct VersionMetadata: Codable {
        var version: String
}

let client = try PostgreSQLConnection.connect(hostname: "localhost", port: 5432, on: group).wait()
_ = try client.authenticate(username: "vapor", database: "test", password: "password").wait()
client.logger = DatabaseLogger(database: .psql, handler: PrintLogHandler())

let results = try client.select().column(.function("version", [])).all(decoding: VersionMetadata.self).wait()
print(results[0].version)

Could be:

import PostgreSQL  // @vapor ~> 1.0

But either works fine.