Nightscout - Boot Error

Unable to connect to Mongo
{"stack":"Error: MongoDB connection string is missing. Please set MONGO_CONNECTION environment variable
at maybe_connect (/app/lib/storage/mongo-storage.js:23:15)
at init (/app/lib/storage/mongo-storage.js:77:10)
at setupStorage (/app/lib/server/bootevent.js:117:44)
at Object. (/app/node_modules/bootevent/index.js:12:7)
at EventEmitter.saw.nest (/app/node_modules/chainsaw/index.js:86:12)
at Object.acquire (/app/node_modules/bootevent/index.js:10:9)
at saw.next (/app/node_modules/chainsaw/index.js:62:18)
at augmentSettings (/app/lib/server/bootevent.js:94:7)
at Object. (/app/node_modules/bootevent/index.js:12:7)
at EventEmitter.saw.nest (/app/node_modules/chainsaw/index.js:86:12)","message":"MongoDB connection string is missing. Please set MONGO_CONNECTION environment variable"}