Imports of nilness command

PathSynopsis
golang.org/x/tools/go/analysis/passes/nilnessPackage nilness inspects the control-flow graph of an SSA function and reports errors such as nil pointer dereferences and degenerate nil pointer comparisons.
golang.org/x/tools/go/analysis/singlecheckerPackage singlechecker defines the main function for an analysis driver with only a single analysis.