api: Add go files

I know this is a huge commit, but I can't be bothered to check
this in part by part.

api/database_connect.go

@@ -0,0 +1,39 @@
+package main
+
+import (
+	"database/sql"
+	_ "github.com/lib/pq"
+	"os"
+)
+
+func connectDB() error {
+	con := os.Getenv("POSTGRES")
+	logger.Infof("opening connection to postgres: %s", con)
+
+	var err error
+	db, err = sql.Open("postgres", con)
+	if err != nil {
+		logger.Errorf("cannot open connection to postgres: %v", err)
+		return err
+	}
+
+	statement := `
+    CREATE TABLE IF NOT EXISTS migrations (
+      filename TEXT NOT NULL UNIQUE
+    );
+  `
+	_, err = db.Exec(statement)
+	if err != nil {
+		logger.Errorf("cannot create migrations table: %v", err)
+		return err
+	}
+
+	// At most 1000 database connections will be left open in the idle state. This
+	// was found to be important when benchmarking with `wrk`: if this was unset,
+	// too many open idle connections were present, resulting in dropped requests
+	// due to the limit on the number of file handles. On benchmarking, around
+	// 100 was found to be pretty optimal.
+	db.SetMaxIdleConns(100)
+
+	return nil
+}