Reports declarations of variables that overlap with the declarations in the outer scope.

As the meaning of the variable depends on the scope in that case, it may create confusion and lead to unintended consequences.

Example:

for i := 0; i < len(nums); i++ {
    for i := 0; i < len(nums); i++ {
    }
  }

The i variable in the embedded loop is shadowed. To get rid of shadowing, consider renaming the variable in the embedded loop.

for i := 0; i < len(nums); i++ {
    for j := 0; j < len(nums); j++ {
    }
  }