Connecting to a database

To store and retrieve cats, we'll need to connect to a database. We'll use PostgreSQL for that purpose, although using another SQL database won't be any different.

First, we'll need a new library to connect to the database. We'll use the Exposed library, which is also developed by JetBrains.

Let's add the following dependency to our build.gradle.kts file:

dependencies {
    implementation("org.jetbrains.exposed:exposed:0.17.14")
    implementation("org.postgresql:postgresql:42.2.24")
    ...
}

Once the libraries are in place, we need to connect to them. To do that, let's create a new file called DB.kt under /src/main/kotlin with the following contents:

object DB {
    private val host=System.getenv("DB_HOST")?:"localhost"
    private val port =     ...