The psalmist knows God is good and that everything that comes from him is good. Notice these:
God treats him with the good (119:65).
Teach me good taste (66).
God is good and beneficent (68).
The humble experiences of his life have even been good (71).
The law is gooder, that is, better than gold (72). [Same word in Hebrew.]
God is good; God therefore treats us with the good; we need to know the good; we learn the good; the Word is “gooder” than gold.