Your config file should be placed at /etc/10man-api/config.
# http listen address
http-address 127.0.0.1:8080
# Connection string for the database (required)
connection-string postgresql://user:pass@localhost/db?sslmode=disable
# Comma separated list of steamID64 for users that should become an admin
admins STEAMID64_ADMIN1,STEAMID64_ADMIN2
# Comma separated list of maps
maps inferno,mirage