I'm currently playing a Bladelock, planning Fighter 1/Warlock 19. Started Fighter 1, Variant Human, Polearm Master feat, Quarterstaff and shield, Dueling fighting style, which makes for a really fun time even at Level 1, with two attacks doing 1d6+2+str on the first and 1d4+2+str on the second, plus an opportunity attack if someone enters melee range, and 18AC, quickly going to 19AC when you get Splint, coupled with Second Wind for early tankiness. For stats, I started 16Str,10Dex,14Con,8Int,8Wis,16Cha.
The Polearm Master bonus action attack (when you aren't casting/transferring Hex) gets you to 3 attacks at level 6 when you get Thirsting Blade, which maximizes Hex, Dueling, Lifedrinker and magic weapons, and IMO is what brings the bladelock out of too-weak territory.
If you don't like quarterstaff with your shield, you can go Roman-style and re-skin it as a short spear, or you could also go Glaive/Halberd and Defensive fighting style for 1 less AC, and 2 fewer damage on your bonus attack, but you get 10ft reach to combo with Warcaster and Repelling Blast for reaction knockback zoning shenanigans starting at character level 5.
I highly recommend the Fiend patron for the temp HP after a kill at Warlock 1, once per short rest add a d10 to an ability check or save at Warlock 6, and resistance to one damage type at Warlock 10, which all synergize well with a melee Bladelock. Also, complement your single target melee attacks with nice ranged/AOE damaging spells like burning hands and fireball, and at Warlock 14, Hurl Through Hell is awesome with no-save CC and a respectable 10d10 psychic damage. Flavor-wise, I also really like the morally questionable issue of a non-evil character with a fiend patron - Is it more of a possession than a pact? Using evil power to fight evil? Maybe you sacrifice your own innocence/purity/soul to protect others?
Take the Warcaster feat at Warlock level 4, which, since you are melee, is a must to help maintain concentration on your Hex or Darkness, lets you cast spells with your hands full of shield and quarterstaff, and combos well with polearm master to cast spells with your reaction when bad guys walk up to you, though it's a little less of a wombo-combo without the glaive/halberd reach, since you have disadvantage to ranged spells like your Repelling+Agonizing Eldritch Blast within 5ft - unless you are in darkness
, but I find that the Frostbite cantrip (EE) works well here (since they are probably about to attack someone), and any single target melee spells or spells with saves are also fine.
After Warcaster, max Strength first, then Charisma.
The Devil's Sight invocation is a must, and combined with Darkness, makes you a monster against anything without blindsight. In addition to giving you advantage on your attacks, Darkness gives attacks against you disadvantage, and since everyone else is both blind & invisible, they cancel each other out, and it doesn't usually affect your group negatively, except you have to tell them where the bad guys are. It can get rid of disadvantage or advantage since one advantage cancels out all disadvantages, and vice-versa. This can work for or against you. Also, in a ranged fight, your allies can exit the darkness, attack targets outside the darkness normally, and return to the darkness for safety.
As mentioned above, complete your build with the bladelock-mandatory invocations Thirsting Blade at Warlock 5 and Lifedrinker at Warlock 12, and Agonizing Blast and Repelling Blast are also good to help round out your kit.
