Add Clibpq as a dependency in your Package.swift file:
// swift-tools-version:4.0
// The swift-tools-version declares the minimum version of Swift required to build this package.
import PackageDescription
letpackage=Package(
name:"foo-bar",
products:[.executable(name:"foo-bar", targets:["foo-bar"]),],
dependencies:[.package(url:"https://github.com/ManuW/Clibpq", from:"0.0.3")],
targets:[
// Targets are the basic building blocks of a package. A target can define a module or a test suite.
// Targets can depend on other targets in this package, and on products in packages which this package depends on.
.target(
name:"foo-bar",
dependencies:[]),])