You can get it with MOI.get(model, MOI.RelativeGap()), see Reference · MathOptInterface, Query Solution Time and RelativeGap() calculation inconsistency · Issue #590 · jump-dev/MathOptInterface.jl · GitHub.
You can get it with MOI.get(model, MOI.RelativeGap()), see Reference · MathOptInterface, Query Solution Time and RelativeGap() calculation inconsistency · Issue #590 · jump-dev/MathOptInterface.jl · GitHub.