If you have a 20 Amp 120 Volt Duplex recepticle
The one on the left, then you are fine to run your Shapeoko. The 20A 120V circuit will safely run anything with a 15 Amp Plug. And as stated above it should be on 12 gauge wire. 15A 120VAC are wired with 14 gauge. It is important that you power off that outlet, and verify it is off, and pull the plug out and verify you have 12 gauge wire. If it is 14 gauge wire then you need to replace the receptacle with a 15 Amp duplex.
The reason this is important is for safety. 15 Amp circuits run safely on 14 gauge wire and 20 Amp circuits run safely on 12 gauge. When you have a 20 amp outlet but only 14 gauge wire attached to it is the heat generated by 20 amps max load could melt your insulation and start a fire from exposed wires.
Depending on when your home was built but the electrical code require that garages and shops use GFCI and any areas that can be wet. You can either have the whole circuit protected with a GFCI breaker or the first outlet in a branch circuit have a GFCI outlet and would protect that circuit and all outlets down stream. GFCI (Ground Fault Circuit Interrupter) protects you in the event of any shorting of neutral or hot which could result in a shock. To identify how many outlets are on a branch circuit plug up a light, fan or other appliance that you can visually tell it is on. Then shut down your breaker and see if the small appliances go off. You can have 8-13 outlets on a single branch circuit so assume there will be multiple outlets on a single branch circuit.
So make sure your 20 amp circuit is got the proper wire and how many other outlets are on that branch circuit. Make sure it is protected by GFCI of the appropriate amperage 15 or 20.
Wire thickness 12 and 14 Gauge
12 Gauge Wire 0.1040 in 2.052 mm
14 Gauge Wire 0.0800 in 1.626 mm
If you do not feel comfortable with this checking then get an electrician to do it.