Go adoption of Norvig's blog post: "Solving Every Sudoku Puzzle"
It small Sudoku solver that demonstrates power of Constraint Propagation and Search;
By default the solver cmd returns a line with solution, which you could pass along to another CLI tool or send to frontend.
-human flag prints out human friendly Sudoko table
$> go run cmd/solver/main.go -human 003020600900305001001806400008102900700000008006708200002609500800203009005010300
4 8 3| 9 2 1| 6 5 7
9 6 7| 3 4 5| 8 2 1
2 5 1| 8 7 6| 4 9 3
------+------+------
5 4 8| 1 3 2| 9 7 6
7 2 9| 5 6 4| 1 3 8
1 3 6| 7 9 8| 2 4 5
------+------+------
3 7 2| 6 8 9| 5 1 4
8 1 4| 2 5 3| 7 6 9
6 9 5| 4 1 7| 3 8 2
# run all integration test against hard problems
go test -v -run TestSudokuSolve